diff --git a/CLAUDE.md b/CLAUDE.md
index b90f102..843d61d 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -205,8 +205,28 @@ pushpull's fully-static order×bound compile is nightly
   which category a dependency is in, not about lookup.
   `tools/normalise-include-delimiters.py --check` enforces it, and also checks
   the converse: every quoted include must resolve beside its includer.
+- **`#pragma once` on line 1 of every header — no `#ifndef` include guards.**
+  Line 1 with no exception, licence and provenance comments included; they keep
+  their text and sit one line lower. **`include/fastfields/core/dlpack.h` is
+  the one exception and must keep its upstream `DLPACK_DLPACK_H_` guard** — it
+  is a verbatim vendored copy, and that macro is what lets it and a *system*
+  DLPack header carrying the same guard collapse into one inclusion, which
+  `#pragma once` cannot do for two distinct files. Do not "finish the job" on
+  it. The seven other headers with third-party provenance (`impl/kernels/`'s
+  `atomic.h`, `parallel{,_impl}.h`, `threadpool.{h,inl}`, `distance/mesh.h`,
+  and `impl/cuda/utils.h`) are adaptations, not drop-in copies: each is
+  re-namespaced into `ff::` and none carries an upstream guard macro, so there
+  is nothing for a guard to interoperate with and the pragma applies to them.
+  A partial-file `#ifndef` is *not* a header guard and this rule leaves it
+  alone — `FF_LIB_BOUND_SPLINE_T` (eight `api/*.h` headers share it so they
+  co-include; `fastfields-dlpack`'s `ext.cpp` depends on that and says so) and
+  the `FF_*_MAX_NBATCH` / `FF_AUTOCAST_PINNED_HOST` build knobs all stay.
+  Enforced by `tools/normalise-header-guards.py --check`, which also applies
+  the convention and audits that no guard macro is tested from another file —
+  the one way deleting a `#define` could change what compiles.
 - `include/fastfields/core/dlpack.h` is vendored upstream code: do not edit it,
-  and it is skipped by `codespell` (see `.codespellrc`).
+  and it is skipped by `codespell` (see `.codespellrc`). It is the only
+  verbatim third-party file in the tree.
 
 ## Pointers
 
diff --git a/include/fastfields/api/checks.h b/include/fastfields/api/checks.h
index 6b41d68..f4f417a 100644
--- a/include/fastfields/api/checks.h
+++ b/include/fastfields/api/checks.h
@@ -1,5 +1,4 @@
-#ifndef FF_LIB_CHECKS
-#define FF_LIB_CHECKS
+#pragma once
 #include <stdexcept>
 #include <fastfields/core/dlpack.h>
 #include <fastfields/core/defines.h>
@@ -56,5 +55,3 @@ inline void require_same_device(const DLTensor & ref, const DLTensor & t, const
 }
 
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_LIB_CHECKS
diff --git a/include/fastfields/api/cpu/distance.h b/include/fastfields/api/cpu/distance.h
index 9382753..ff9da0c 100644
--- a/include/fastfields/api/cpu/distance.h
+++ b/include/fastfields/api/cpu/distance.h
@@ -1,5 +1,4 @@
-#ifndef FF_CPU_DISTANCE
-#define FF_CPU_DISTANCE
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -62,5 +61,3 @@ void dt_mesh(
 
 } // namespace cpu
 } // namespace ff
-
-#endif // FF_CPU_DISTANCE
diff --git a/include/fastfields/api/cpu/posdef.h b/include/fastfields/api/cpu/posdef.h
index 74452e5..8f95b1e 100644
--- a/include/fastfields/api/cpu/posdef.h
+++ b/include/fastfields/api/cpu/posdef.h
@@ -1,5 +1,4 @@
-#ifndef FF_CPU_POSDEF
-#define FF_CPU_POSDEF
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -80,5 +79,3 @@ void sym_invert_(
 
 } // namespace cpu
 } // namespace ff
-
-#endif // FF_CPU_POSDEF
diff --git a/include/fastfields/api/cpu/pushpull.h b/include/fastfields/api/cpu/pushpull.h
index 6a33df3..7141233 100644
--- a/include/fastfields/api/cpu/pushpull.h
+++ b/include/fastfields/api/cpu/pushpull.h
@@ -1,5 +1,4 @@
-#ifndef FF_CPU_PUSHPULL
-#define FF_CPU_PUSHPULL
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -199,5 +198,3 @@ void grad_backward(
 
 } // namespace cpu
 } // namespace ff
-
-#endif // FF_CPU_PUSHPULL
diff --git a/include/fastfields/api/cpu/pushpull_dispatch.h b/include/fastfields/api/cpu/pushpull_dispatch.h
index a05e64c..a6383b4 100644
--- a/include/fastfields/api/cpu/pushpull_dispatch.h
+++ b/include/fastfields/api/cpu/pushpull_dispatch.h
@@ -1,5 +1,4 @@
-#ifndef FF_CPU_PUSHPULL_DISPATCH
-#define FF_CPU_PUSHPULL_DISPATCH
+#pragma once
 /**
  * Private (not installed) header: the argument-marshalling helpers, the
  * argument checks and the ndim x order x bound x dtype dispatch matrix
@@ -103,5 +102,3 @@ typedef double reduce_t;
 
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_CPU_PUSHPULL_DISPATCH
diff --git a/include/fastfields/api/cpu/reg_field.h b/include/fastfields/api/cpu/reg_field.h
index ed3abb5..6d5e005 100644
--- a/include/fastfields/api/cpu/reg_field.h
+++ b/include/fastfields/api/cpu/reg_field.h
@@ -1,5 +1,4 @@
-#ifndef FF_CPU_REG_FIELD
-#define FF_CPU_REG_FIELD
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -368,5 +367,3 @@ void field_relax_rls(
 
 } // namespace cpu
 } // namespace ff
-
-#endif // FF_CPU_REG_FIELD
diff --git a/include/fastfields/api/cpu/reg_flow.h b/include/fastfields/api/cpu/reg_flow.h
index e19c798..cbf300c 100644
--- a/include/fastfields/api/cpu/reg_flow.h
+++ b/include/fastfields/api/cpu/reg_flow.h
@@ -1,5 +1,4 @@
-#ifndef FF_CPU_REG_FLOW
-#define FF_CPU_REG_FLOW
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -404,5 +403,3 @@ void flow_relax_rls(
 
 } // namespace cpu
 } // namespace ff
-
-#endif // FF_CPU_REG_FLOW
diff --git a/include/fastfields/api/cpu/resize.h b/include/fastfields/api/cpu/resize.h
index e67ef75..8734d0e 100644
--- a/include/fastfields/api/cpu/resize.h
+++ b/include/fastfields/api/cpu/resize.h
@@ -1,5 +1,4 @@
-#ifndef FF_CPU_RESIZE
-#define FF_CPU_RESIZE
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -38,5 +37,3 @@ void resample(
 
 } // namespace cpu
 } // namespace ff
-
-#endif // FF_CPU_RESIZE
diff --git a/include/fastfields/api/cpu/restrict.h b/include/fastfields/api/cpu/restrict.h
index a1c0c95..cab6c1d 100644
--- a/include/fastfields/api/cpu/restrict.h
+++ b/include/fastfields/api/cpu/restrict.h
@@ -1,5 +1,4 @@
-#ifndef FF_CPU_RESTRICT
-#define FF_CPU_RESTRICT
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -40,5 +39,3 @@ void restriction(
 
 } // namespace cpu
 } // namespace ff
-
-#endif // FF_CPU_RESTRICT
diff --git a/include/fastfields/api/cpu/solve_field.h b/include/fastfields/api/cpu/solve_field.h
index 31d4ec3..3e7367e 100644
--- a/include/fastfields/api/cpu/solve_field.h
+++ b/include/fastfields/api/cpu/solve_field.h
@@ -1,5 +1,4 @@
-#ifndef FF_CPU_SOLVE_FIELD
-#define FF_CPU_SOLVE_FIELD
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -66,5 +65,3 @@ void field_cg(
 
 } // namespace cpu
 } // namespace ff
-
-#endif // FF_CPU_SOLVE_FIELD
diff --git a/include/fastfields/api/cpu/splinc.h b/include/fastfields/api/cpu/splinc.h
index f2acc00..751a369 100644
--- a/include/fastfields/api/cpu/splinc.h
+++ b/include/fastfields/api/cpu/splinc.h
@@ -1,5 +1,4 @@
-#ifndef FF_CPU_SPLINC
-#define FF_CPU_SPLINC
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -28,5 +27,3 @@ void spline_coeff(
 
 } // namespace cpu
 } // namespace ff
-
-#endif // FF_CPU_SPLINC
diff --git a/include/fastfields/api/cuda/distance.h b/include/fastfields/api/cuda/distance.h
index 70b8350..42aa97e 100644
--- a/include/fastfields/api/cuda/distance.h
+++ b/include/fastfields/api/cuda/distance.h
@@ -1,5 +1,4 @@
-#ifndef FF_CUDA_DISTANCE
-#define FF_CUDA_DISTANCE
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -62,5 +61,3 @@ void dt_mesh(
 
 } // namespace cuda
 } // namespace ff
-
-#endif // FF_CUDA_DISTANCE
diff --git a/include/fastfields/api/cuda/posdef.h b/include/fastfields/api/cuda/posdef.h
index 7f3cab6..339f8fc 100644
--- a/include/fastfields/api/cuda/posdef.h
+++ b/include/fastfields/api/cuda/posdef.h
@@ -1,5 +1,4 @@
-#ifndef FF_CUDA_POSDEF
-#define FF_CUDA_POSDEF
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -80,5 +79,3 @@ void sym_invert_(
 
 } // namespace cuda
 } // namespace ff
-
-#endif // FF_CUDA_POSDEF
diff --git a/include/fastfields/api/cuda/pushpull.h b/include/fastfields/api/cuda/pushpull.h
index 4f64e26..732c16f 100644
--- a/include/fastfields/api/cuda/pushpull.h
+++ b/include/fastfields/api/cuda/pushpull.h
@@ -1,5 +1,4 @@
-#ifndef FF_CUDA_PUSHPULL
-#define FF_CUDA_PUSHPULL
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -199,5 +198,3 @@ void grad_backward(
 
 } // namespace cuda
 } // namespace ff
-
-#endif // FF_CUDA_PUSHPULL
diff --git a/include/fastfields/api/cuda/pushpull_dispatch.h b/include/fastfields/api/cuda/pushpull_dispatch.h
index 23c048c..34c9749 100644
--- a/include/fastfields/api/cuda/pushpull_dispatch.h
+++ b/include/fastfields/api/cuda/pushpull_dispatch.h
@@ -1,5 +1,4 @@
-#ifndef FF_CUDA_PUSHPULL_DISPATCH
-#define FF_CUDA_PUSHPULL_DISPATCH
+#pragma once
 /**
  * Private (not installed) header: the argument-marshalling helpers, the
  * argument checks and the ndim x order x bound x dtype dispatch matrix
@@ -92,5 +91,3 @@ typedef double reduce_t;
 
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_CUDA_PUSHPULL_DISPATCH
diff --git a/include/fastfields/api/cuda/reg_field.h b/include/fastfields/api/cuda/reg_field.h
index f797a9b..330351b 100644
--- a/include/fastfields/api/cuda/reg_field.h
+++ b/include/fastfields/api/cuda/reg_field.h
@@ -1,5 +1,4 @@
-#ifndef FF_CUDA_REG_FIELD
-#define FF_CUDA_REG_FIELD
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -332,5 +331,3 @@ void field_relax_rls(
 
 } // namespace cuda
 } // namespace ff
-
-#endif // FF_CUDA_REG_FIELD
diff --git a/include/fastfields/api/cuda/reg_flow.h b/include/fastfields/api/cuda/reg_flow.h
index 8c7d78f..7d703c6 100644
--- a/include/fastfields/api/cuda/reg_flow.h
+++ b/include/fastfields/api/cuda/reg_flow.h
@@ -1,5 +1,4 @@
-#ifndef FF_CUDA_REG_FLOW
-#define FF_CUDA_REG_FLOW
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -359,5 +358,3 @@ void flow_relax_rls(
 
 } // namespace cuda
 } // namespace ff
-
-#endif // FF_CUDA_REG_FLOW
diff --git a/include/fastfields/api/cuda/resize.h b/include/fastfields/api/cuda/resize.h
index 119f3bf..90df298 100644
--- a/include/fastfields/api/cuda/resize.h
+++ b/include/fastfields/api/cuda/resize.h
@@ -1,5 +1,4 @@
-#ifndef FF_CUDA_RESIZE
-#define FF_CUDA_RESIZE
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -38,5 +37,3 @@ void resample(
 
 } // namespace cuda
 } // namespace ff
-
-#endif // FF_CUDA_RESIZE
diff --git a/include/fastfields/api/cuda/restrict.h b/include/fastfields/api/cuda/restrict.h
index d75a99b..ac7c4c3 100644
--- a/include/fastfields/api/cuda/restrict.h
+++ b/include/fastfields/api/cuda/restrict.h
@@ -1,5 +1,4 @@
-#ifndef FF_CUDA_RESTRICT
-#define FF_CUDA_RESTRICT
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -40,5 +39,3 @@ void restriction(
 
 } // namespace cuda
 } // namespace ff
-
-#endif // FF_CUDA_RESTRICT
diff --git a/include/fastfields/api/cuda/splinc.h b/include/fastfields/api/cuda/splinc.h
index 5cc7c12..f174c9b 100644
--- a/include/fastfields/api/cuda/splinc.h
+++ b/include/fastfields/api/cuda/splinc.h
@@ -1,5 +1,4 @@
-#ifndef FF_CUDA_SPLINC
-#define FF_CUDA_SPLINC
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 
@@ -28,5 +27,3 @@ void spline_coeff(
 
 } // namespace cuda
 } // namespace ff
-
-#endif // FF_CUDA_SPLINC
diff --git a/include/fastfields/api/cuda/stream.h b/include/fastfields/api/cuda/stream.h
index 07a6ead..b5745e5 100644
--- a/include/fastfields/api/cuda/stream.h
+++ b/include/fastfields/api/cuda/stream.h
@@ -1,7 +1,4 @@
 #pragma once
-#ifndef FF_CUDA_STREAM
-#define FF_CUDA_STREAM
-
 /**
  * The public ABI carries a CUDA stream as an `intptr_t` (no CUDA types leak
  * into the exported signatures); the cuda-impl launchers take a real
@@ -29,5 +26,3 @@ static inline cudaStream_t _reg_stream(intptr_t stream)
 
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_CUDA_STREAM
diff --git a/include/fastfields/api/distance.h b/include/fastfields/api/distance.h
index 1d9a2db..9c5374e 100644
--- a/include/fastfields/api/distance.h
+++ b/include/fastfields/api/distance.h
@@ -1,5 +1,4 @@
-#ifndef FF_LIB_DISTANCE
-#define FF_LIB_DISTANCE
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 #include <fastfields/core/defines.h>
@@ -176,5 +175,3 @@ void dt_mesh(
 );
 
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_LIB_DISTANCE
diff --git a/include/fastfields/api/posdef.h b/include/fastfields/api/posdef.h
index 666454a..35d1582 100644
--- a/include/fastfields/api/posdef.h
+++ b/include/fastfields/api/posdef.h
@@ -1,5 +1,4 @@
-#ifndef FF_LIB_POSDEF
-#define FF_LIB_POSDEF
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 #include <fastfields/core/defines.h>
@@ -80,5 +79,3 @@ void sym_invert_(
 );
 
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_LIB_POSDEF
diff --git a/include/fastfields/api/pushpull.h b/include/fastfields/api/pushpull.h
index f71ebb2..19883b7 100644
--- a/include/fastfields/api/pushpull.h
+++ b/include/fastfields/api/pushpull.h
@@ -1,5 +1,4 @@
-#ifndef FF_LIB_PUSHPULL
-#define FF_LIB_PUSHPULL
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 #include <fastfields/core/defines.h>
@@ -228,5 +227,3 @@ void grad_backward(
 );
 
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_LIB_PUSHPULL
diff --git a/include/fastfields/api/reg_field.h b/include/fastfields/api/reg_field.h
index 3b43c1b..c8d39f8 100644
--- a/include/fastfields/api/reg_field.h
+++ b/include/fastfields/api/reg_field.h
@@ -1,5 +1,4 @@
-#ifndef FF_LIB_REG_FIELD
-#define FF_LIB_REG_FIELD
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 #include <fastfields/core/defines.h>
@@ -376,5 +375,3 @@ void field_relax_rls(
 );
 
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_LIB_REG_FIELD
diff --git a/include/fastfields/api/reg_flow.h b/include/fastfields/api/reg_flow.h
index 5b42602..7d185f3 100644
--- a/include/fastfields/api/reg_flow.h
+++ b/include/fastfields/api/reg_flow.h
@@ -1,5 +1,4 @@
-#ifndef FF_LIB_REG_FLOW
-#define FF_LIB_REG_FLOW
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 #include <fastfields/core/defines.h>
@@ -397,5 +396,3 @@ void flow_relax_rls(
 );
 
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_LIB_REG_FLOW
diff --git a/include/fastfields/api/resize.h b/include/fastfields/api/resize.h
index c8de089..fe75ccd 100644
--- a/include/fastfields/api/resize.h
+++ b/include/fastfields/api/resize.h
@@ -1,5 +1,4 @@
-#ifndef FF_LIB_RESIZE
-#define FF_LIB_RESIZE
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 #include <fastfields/core/defines.h>
@@ -68,5 +67,3 @@ void resample(
 );
 
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_LIB_RESIZE
diff --git a/include/fastfields/api/restrict.h b/include/fastfields/api/restrict.h
index 7461f71..19d731d 100644
--- a/include/fastfields/api/restrict.h
+++ b/include/fastfields/api/restrict.h
@@ -1,5 +1,4 @@
-#ifndef FF_LIB_RESTRICT
-#define FF_LIB_RESTRICT
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 #include <fastfields/core/defines.h>
@@ -67,5 +66,3 @@ void restriction(
 );
 
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_LIB_RESTRICT
diff --git a/include/fastfields/api/solve_field.h b/include/fastfields/api/solve_field.h
index 6bc8c21..8b7652c 100644
--- a/include/fastfields/api/solve_field.h
+++ b/include/fastfields/api/solve_field.h
@@ -1,5 +1,4 @@
-#ifndef FF_LIB_SOLVE_FIELD
-#define FF_LIB_SOLVE_FIELD
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <fastfields/core/defines.h>
 
@@ -93,5 +92,3 @@ void field_cg(
 );
 
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_LIB_SOLVE_FIELD
diff --git a/include/fastfields/api/splinc.h b/include/fastfields/api/splinc.h
index 07f32fa..ba00472 100644
--- a/include/fastfields/api/splinc.h
+++ b/include/fastfields/api/splinc.h
@@ -1,5 +1,4 @@
-#ifndef FF_LIB_SPLINC
-#define FF_LIB_SPLINC
+#pragma once
 #include <fastfields/core/dlpack.h>
 #include <cstdint>
 #include <stdexcept>
@@ -114,5 +113,3 @@ void spline_coeff(
 );
 
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_LIB_SPLINC
diff --git a/include/fastfields/core/autocast.h b/include/fastfields/core/autocast.h
index e730a66..6886480 100644
--- a/include/fastfields/core/autocast.h
+++ b/include/fastfields/core/autocast.h
@@ -1,6 +1,4 @@
 #pragma once
-#ifndef FF_AUTOCAST
-#define FF_AUTOCAST
 #include <cstddef>
 #include <cstdint>
 #include <fastfields/core/dlpack.h>
@@ -199,5 +197,3 @@ inline void free_if_needed(OutPointer ptr)
 
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_AUTOCAST
diff --git a/include/fastfields/core/cuda_switch.h b/include/fastfields/core/cuda_switch.h
index e302a00..23ea881 100755
--- a/include/fastfields/core/cuda_switch.h
+++ b/include/fastfields/core/cuda_switch.h
@@ -1,8 +1,4 @@
 #pragma once
-#ifndef FF_CUDA_SWITCH
-#define FF_CUDA_SWITCH
-
-
 #ifndef __CUDACC__
 
 // replace __device__ with empty symbol
@@ -50,5 +46,3 @@
 #endif
 
 #include <fastfields/core/defines.h>
-
-#endif // FF_CUDA_SWITCH
diff --git a/include/fastfields/core/defines.h b/include/fastfields/core/defines.h
index 3bc5819..d567ce2 100644
--- a/include/fastfields/core/defines.h
+++ b/include/fastfields/core/defines.h
@@ -1,7 +1,4 @@
 #pragma once
-#ifndef FF_DEFINES
-#define FF_DEFINES
-
 // Merged from fastfields-kernels/defines.h and fastfields-lib/defines.h during
 // the six-repo consolidation. The first three macros were token-identical in
 // both; the namespace-device pair came from kernels and the FF_CPU/FF_CUDA pair
@@ -34,5 +31,3 @@
 #else
 #  define FF_CUDA cuda
 #endif
-
-#endif // FF_DEFINES
diff --git a/include/fastfields/core/dispatch.h b/include/fastfields/core/dispatch.h
index 5862aed..1a0073b 100644
--- a/include/fastfields/core/dispatch.h
+++ b/include/fastfields/core/dispatch.h
@@ -1,7 +1,4 @@
 #pragma once
-#ifndef FF_CORE_DISPATCH
-#define FF_CORE_DISPATCH
-
 /**
  * The helpers shared by both dtype-dispatch layers (`src/lib-cpu` and
  * `src/lib-cuda`): unpack the public pointer ABI's arguments into what the
@@ -228,5 +225,3 @@ inline std::vector<double> as_weights(const double * w, int64_t nc)
 }
 
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_CORE_DISPATCH
diff --git a/include/fastfields/impl/cpu/distance_euclidean.h b/include/fastfields/impl/cpu/distance_euclidean.h
index c55f9f2..e9cf7b5 100755
--- a/include/fastfields/impl/cpu/distance_euclidean.h
+++ b/include/fastfields/impl/cpu/distance_euclidean.h
@@ -1,5 +1,4 @@
-#ifndef FF_CPU_DISTANCE_EUCLIDEAN
-#define FF_CPU_DISTANCE_EUCLIDEAN
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include <fastfields/impl/kernels/distance.h>
 #include <fastfields/impl/kernels/batch.h>
@@ -56,5 +55,3 @@ dt(
 FF_NAMESPACE_END(distance_e)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_CPU_DISTANCE_EUCLIDEAN
diff --git a/include/fastfields/impl/cpu/distance_l1.h b/include/fastfields/impl/cpu/distance_l1.h
index 3a5a5b2..ea8b0af 100755
--- a/include/fastfields/impl/cpu/distance_l1.h
+++ b/include/fastfields/impl/cpu/distance_l1.h
@@ -1,5 +1,4 @@
-#ifndef FF_CPU_DISTANCE_L1
-#define FF_CPU_DISTANCE_L1
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include <fastfields/impl/kernels/distance.h>
 #include <fastfields/impl/kernels/batch.h>
@@ -35,5 +34,3 @@ dt(
 FF_NAMESPACE_END(distance_l1)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_CPU_DISTANCE_L1
diff --git a/include/fastfields/impl/cpu/distance_mesh.h b/include/fastfields/impl/cpu/distance_mesh.h
index 7484800..53eaf89 100755
--- a/include/fastfields/impl/cpu/distance_mesh.h
+++ b/include/fastfields/impl/cpu/distance_mesh.h
@@ -1,5 +1,4 @@
-#ifndef FF_CPU_DISTANCE_MESH
-#define FF_CPU_DISTANCE_MESH
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include <fastfields/impl/kernels/distance.h>
 #include <fastfields/impl/kernels/distance/mesh_utils.h>
@@ -714,6 +713,3 @@ dt(
 FF_NAMESPACE_END(distance_mesh)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-
-#endif // FF_DISTANCE_MESH
diff --git a/include/fastfields/impl/cpu/distance_spline.h b/include/fastfields/impl/cpu/distance_spline.h
index a04e340..6d3799a 100755
--- a/include/fastfields/impl/cpu/distance_spline.h
+++ b/include/fastfields/impl/cpu/distance_spline.h
@@ -1,5 +1,4 @@
-#ifndef FF_CPU_DISTANCE_SPLINE
-#define FF_CPU_DISTANCE_SPLINE
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include <fastfields/impl/kernels/distance.h>
 #include <fastfields/impl/kernels/batch.h>
@@ -182,5 +181,3 @@ mindist_gaussnewton(
 FF_NAMESPACE_END(distance_spline)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_CPU_DISTANCE_SPLINE
diff --git a/include/fastfields/impl/cpu/posdef.h b/include/fastfields/impl/cpu/posdef.h
index a467164..9a55849 100755
--- a/include/fastfields/impl/cpu/posdef.h
+++ b/include/fastfields/impl/cpu/posdef.h
@@ -1,5 +1,4 @@
-#ifndef FF_POSDEF_CPU
-#define FF_POSDEF_CPU
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include <fastfields/impl/kernels/posdef.h>
 #include <fastfields/impl/kernels/batch.h>
@@ -466,5 +465,3 @@ void sym_invert_(
 FF_NAMESPACE_END(posdef)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_POSDEF_CPU
diff --git a/include/fastfields/impl/cpu/pushpull.h b/include/fastfields/impl/cpu/pushpull.h
index 89bd380..fff4ccb 100755
--- a/include/fastfields/impl/cpu/pushpull.h
+++ b/include/fastfields/impl/cpu/pushpull.h
@@ -1,5 +1,4 @@
-#ifndef FF_PUSHPULL_CPU
-#define FF_PUSHPULL_CPU
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include <fastfields/impl/kernels/pushpull.h>
 #include <fastfields/impl/kernels/batch.h>
@@ -772,5 +771,3 @@ void grad_backward(
 FF_NAMESPACE_END(pushpull)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_PUSHPULL_CPU
diff --git a/include/fastfields/impl/cpu/reg_field.h b/include/fastfields/impl/cpu/reg_field.h
index 5990f6e..9f838f0 100755
--- a/include/fastfields/impl/cpu/reg_field.h
+++ b/include/fastfields/impl/cpu/reg_field.h
@@ -1,5 +1,4 @@
-#ifndef FF_REGULARISERS_FIELD_CPU
-#define FF_REGULARISERS_FIELD_CPU
+#pragma once
 #include <stdexcept>
 #include <fastfields/core/cuda_switch.h>
 #include <fastfields/impl/kernels/bounds.h>
@@ -1837,5 +1836,3 @@ void relax_bending_jrls_(
 FF_NAMESPACE_END(reg_field)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_REGULARISERS_FIELD_CPU
diff --git a/include/fastfields/impl/cpu/reg_flow.h b/include/fastfields/impl/cpu/reg_flow.h
index f29ec0e..a1a71ce 100755
--- a/include/fastfields/impl/cpu/reg_flow.h
+++ b/include/fastfields/impl/cpu/reg_flow.h
@@ -1,5 +1,4 @@
-#ifndef FF_REGULARISERS_FLOW_CPU
-#define FF_REGULARISERS_FLOW_CPU
+#pragma once
 #include <stdexcept>
 #include <fastfields/core/cuda_switch.h>
 #include <fastfields/impl/kernels/bounds.h>
@@ -1495,6 +1494,3 @@ void relax_lame_jrls_(
 FF_NAMESPACE_END(reg_flow)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-
-#endif // FF_REGULARISERS_FLOW_CPU
diff --git a/include/fastfields/impl/cpu/resize.h b/include/fastfields/impl/cpu/resize.h
index 4973fc1..d90be66 100755
--- a/include/fastfields/impl/cpu/resize.h
+++ b/include/fastfields/impl/cpu/resize.h
@@ -1,5 +1,4 @@
-#ifndef FF_RESIZE_LOOP
-#define FF_RESIZE_LOOP
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include <fastfields/impl/kernels/resize.h>
 #include <fastfields/impl/kernels/batch.h>
@@ -96,5 +95,3 @@ void loopnd(
 FF_NAMESPACE_END(resize)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_RESIZE_LOOP
diff --git a/include/fastfields/impl/cpu/restrict.h b/include/fastfields/impl/cpu/restrict.h
index a3e9798..9b5b848 100755
--- a/include/fastfields/impl/cpu/restrict.h
+++ b/include/fastfields/impl/cpu/restrict.h
@@ -1,5 +1,4 @@
-#ifndef FF_RESTRICT_LOOP
-#define FF_RESTRICT_LOOP
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include <fastfields/impl/kernels/restrict.h>
 #include <fastfields/impl/kernels/batch.h>
@@ -269,5 +268,3 @@ void loopnd(
 FF_NAMESPACE_END(restrict)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_RESTRICT_LOOP
diff --git a/include/fastfields/impl/cpu/solve_field.h b/include/fastfields/impl/cpu/solve_field.h
index 2b06aa0..7c156f8 100644
--- a/include/fastfields/impl/cpu/solve_field.h
+++ b/include/fastfields/impl/cpu/solve_field.h
@@ -1,5 +1,4 @@
-#ifndef FF_SOLVE_FIELD_CPU
-#define FF_SOLVE_FIELD_CPU
+#pragma once
 #include <vector>
 #include <fastfields/core/cuda_switch.h>
 #include <fastfields/impl/kernels/utils.h>
@@ -144,5 +143,3 @@ void axpby_(
 FF_NAMESPACE_END(solve_field)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_SOLVE_FIELD_CPU
diff --git a/include/fastfields/impl/cpu/splinc.h b/include/fastfields/impl/cpu/splinc.h
index 759d525..e9aa227 100755
--- a/include/fastfields/impl/cpu/splinc.h
+++ b/include/fastfields/impl/cpu/splinc.h
@@ -1,5 +1,4 @@
-#ifndef FF_SPLINC_LOOP
-#define FF_SPLINC_LOOP
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include <fastfields/impl/kernels/splinc.h>
 #include <fastfields/impl/kernels/batch.h>
@@ -41,5 +40,3 @@ void loop(
 FF_NAMESPACE_END(splinc)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_SPLINC_LOOP
diff --git a/include/fastfields/impl/cpu/tetrahedron.h b/include/fastfields/impl/cpu/tetrahedron.h
index 0454118..d5a7fdf 100755
--- a/include/fastfields/impl/cpu/tetrahedron.h
+++ b/include/fastfields/impl/cpu/tetrahedron.h
@@ -1,7 +1,4 @@
-#ifndef FF_TETRAHEDRON_LOOP
-#define FF_TETRAHEDRON_LOOP
-
-
+#pragma once
 namespace ff {
 namespace tetra {
 
@@ -80,5 +77,3 @@ void pull(
 
 } // namespace tetra
 } // namespace ff
-
-#endif // FF_TETRAHEDRON_LOOP
diff --git a/include/fastfields/impl/kernels/atomic.h b/include/fastfields/impl/kernels/atomic.h
index 4f9df1e..e184806 100755
--- a/include/fastfields/impl/kernels/atomic.h
+++ b/include/fastfields/impl/kernels/atomic.h
@@ -1,10 +1,9 @@
+#pragma once
 /***********************************************************************
  * CUDA portion copied from PyTorch/ATen
  * https://github.com/pytorch/pytorch/blob/master/LICENSE
  **********************************************************************/
 
-#ifndef FF_ATOMIC
-#define FF_ATOMIC
 #include <fastfields/core/cuda_switch.h>
 
 /***********************************************************************
@@ -362,5 +361,3 @@ static inline FF_CUDEV void anyAtomicAddNoReturn(T *address, T val) {
 } // namespace ff
 
 #endif // __CUDA__
-
-#endif // FF_ATOMIC
diff --git a/include/fastfields/impl/kernels/batch.h b/include/fastfields/impl/kernels/batch.h
index 8cdceea..0f8523b 100755
--- a/include/fastfields/impl/kernels/batch.h
+++ b/include/fastfields/impl/kernels/batch.h
@@ -1,3 +1,4 @@
+#pragma once
 /* Utilities to convert contiguous linear indices to
  * - sub-indices, and/or
  * - strided linear indices
@@ -19,8 +20,6 @@
  * - a dynamically sized version, where `ndim` is a function argument
  * - a statically sized version, where `ndim` is a template parameter
  */
-#ifndef FF_BATCH
-#define FF_BATCH
 #include <fastfields/core/cuda_switch.h>
 #include "utils.h"
 
@@ -269,5 +268,3 @@ void index2sub(
 }
 
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_BATCH
diff --git a/include/fastfields/impl/kernels/bounds.h b/include/fastfields/impl/kernels/bounds.h
index 199f285..555685f 100755
--- a/include/fastfields/impl/kernels/bounds.h
+++ b/include/fastfields/impl/kernels/bounds.h
@@ -1,5 +1,4 @@
-#ifndef FF_BOUNDS
-#define FF_BOUNDS
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "atomic.h"
 #include "utils.h"
@@ -796,5 +795,3 @@ sign(type bound_type, offset_t coord, size_t size) {
 FF_NAMESPACE_END(bound)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_BOUNDS
diff --git a/include/fastfields/impl/kernels/distance.h b/include/fastfields/impl/kernels/distance.h
index 1ff4939..f40a817 100755
--- a/include/fastfields/impl/kernels/distance.h
+++ b/include/fastfields/impl/kernels/distance.h
@@ -1,4 +1,5 @@
+#pragma once
 #include "distance/euclidean.h"
 #include "distance/l1.h"
 #include "distance/spline.h"
-#include "distance/mesh.h"
\ No newline at end of file
+#include "distance/mesh.h"
diff --git a/include/fastfields/impl/kernels/distance/euclidean.h b/include/fastfields/impl/kernels/distance/euclidean.h
index b5a6127..8a01135 100755
--- a/include/fastfields/impl/kernels/distance/euclidean.h
+++ b/include/fastfields/impl/kernels/distance/euclidean.h
@@ -1,3 +1,4 @@
+#pragma once
 // "Distance Transforms of Sampled Functions"
 // Pedro F. Felzenszwalb & Daniel P. Huttenlocher
 // Theory of Computing (2012)
@@ -5,8 +6,6 @@
 //
 // This algorithm works by upper-bounding the Euclidean distance with
 // the lower envelope of a series of parabolas.
-#ifndef FF_DISTANCE_E
-#define FF_DISTANCE_E
 #include <fastfields/core/cuda_switch.h>
 #include "../utils.h"
 
@@ -120,5 +119,3 @@ void kernel(scalar_t * f, offset_t * v, scalar_t * z, scalar_t * d, scalar_t w2,
 FF_NAMESPACE_END(distance_e)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_DISTANCE_E
diff --git a/include/fastfields/impl/kernels/distance/l1.h b/include/fastfields/impl/kernels/distance/l1.h
index f80459d..cfb9529 100755
--- a/include/fastfields/impl/kernels/distance/l1.h
+++ b/include/fastfields/impl/kernels/distance/l1.h
@@ -1,9 +1,8 @@
+#pragma once
 // "Distance Transforms of Sampled Functions"
 // Pedro F. Felzenszwalb & Daniel P. Huttenlocher
 // Theory of Computing (2012)
 // https://www.theoryofcomputing.org/articles/v008a019/v008a019.pdf
-#ifndef FF_DISTANCE_L1
-#define FF_DISTANCE_L1
 #include <fastfields/core/cuda_switch.h>
 #include "../utils.h"
 
@@ -45,4 +44,3 @@ void kernel(scalar_t * f, offset_t size, offset_t stride, scalar_t w)
 FF_NAMESPACE_END(distance_l1)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-#endif // FF_DISTANCE_L1
diff --git a/include/fastfields/impl/kernels/distance/mesh.h b/include/fastfields/impl/kernels/distance/mesh.h
index 0737766..5c771e2 100755
--- a/include/fastfields/impl/kernels/distance/mesh.h
+++ b/include/fastfields/impl/kernels/distance/mesh.h
@@ -1,9 +1,8 @@
+#pragma once
 /*
  * Adapted from
  * https://github.com/InteractiveComputerGraphics/TriangleMeshDistance
  */
-#ifndef FF_DISTANCE_MESH_H
-#define FF_DISTANCE_MESH_H
 #include <fastfields/core/cuda_switch.h>
 #include "../utils.h"
 #include "mesh_utils.h"
@@ -1477,5 +1476,3 @@ struct MeshDist {
 FF_NAMESPACE_END(distance_mesh)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_DISTANCE_MESH_H
diff --git a/include/fastfields/impl/kernels/distance/mesh_utils.h b/include/fastfields/impl/kernels/distance/mesh_utils.h
index c67aaa3..c5735a6 100755
--- a/include/fastfields/impl/kernels/distance/mesh_utils.h
+++ b/include/fastfields/impl/kernels/distance/mesh_utils.h
@@ -1,5 +1,4 @@
-#ifndef FF_DISTANCE_MESH_UTILS_H
-#define FF_DISTANCE_MESH_UTILS_H
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "../utils.h"
 
@@ -1154,5 +1153,3 @@ struct ConstStridedPointArray<D, scalar_t, offset_t> {
 FF_NAMESPACE_END(distance_mesh)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_DISTANCE_MESH_UTILS_H
diff --git a/include/fastfields/impl/kernels/distance/spline.h b/include/fastfields/impl/kernels/distance/spline.h
index df9b174..31593a8 100755
--- a/include/fastfields/impl/kernels/distance/spline.h
+++ b/include/fastfields/impl/kernels/distance/spline.h
@@ -1,5 +1,4 @@
-#ifndef FF_DISTANCE_SPLINE_H
-#define FF_DISTANCE_SPLINE_H
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "../spline.h"
 #include "../bounds.h"
@@ -469,5 +468,3 @@ class Kernels {
 FF_NAMESPACE_END(distance_spline)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_DISTANCE_SPLINE_H
diff --git a/include/fastfields/impl/kernels/meta.h b/include/fastfields/impl/kernels/meta.h
index dcb2705..5ff8741 100644
--- a/include/fastfields/impl/kernels/meta.h
+++ b/include/fastfields/impl/kernels/meta.h
@@ -1,5 +1,4 @@
-#ifndef FF_META
-#define FF_META
+#pragma once
 #include <fastfields/core/defines.h>
 
 FF_NAMESPACE_BEGIN(FF_NS)
@@ -42,6 +41,3 @@ template <int...      D>       using Int             = Tuple<int,      D...>;
 
 FF_NAMESPACE_END(meta)
 FF_NAMESPACE_END(FF_NS)
-
-
-#endif // FF_META
diff --git a/include/fastfields/impl/kernels/parallel.h b/include/fastfields/impl/kernels/parallel.h
index e91a405..8bf6160 100755
--- a/include/fastfields/impl/kernels/parallel.h
+++ b/include/fastfields/impl/kernels/parallel.h
@@ -1,9 +1,8 @@
+#pragma once
 /* LICENSE:
  * Most of the functions are adapted from PyTorch/ATen's ParallelNative
  * https://github.com/pytorch/pytorch/blob/master/LICENSE
  */
-#ifndef FF_PARALLEL_H
-#define FF_PARALLEL_H
 #include <cstdint>
 #include <fastfields/core/defines.h>
 #include "parallel_impl.h"
@@ -51,5 +50,3 @@ inline void parallel_for(int64_t begin, int64_t end, int64_t grain_size, const F
 }
 
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_PARALLEL_H
diff --git a/include/fastfields/impl/kernels/parallel_impl.h b/include/fastfields/impl/kernels/parallel_impl.h
index 2fcdb78..7b1ef12 100755
--- a/include/fastfields/impl/kernels/parallel_impl.h
+++ b/include/fastfields/impl/kernels/parallel_impl.h
@@ -1,9 +1,8 @@
+#pragma once
 /* LICENSE:
  * Most of the functions are adapted from PyTorch/ATen's ParallelNative
  * https://github.com/pytorch/pytorch/blob/master/LICENSE
  */
-#ifndef FF_PARALLEL_IMPL_H
-#define FF_PARALLEL_IMPL_H
 #include <fastfields/core/defines.h>
 #include <queue>
 #include <string>
@@ -231,5 +230,3 @@ FF_NAMESPACE_BEGIN(internal)
 
 FF_NAMESPACE_END(internal)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_PARALLEL_IMPL_H
diff --git a/include/fastfields/impl/kernels/posdef.h b/include/fastfields/impl/kernels/posdef.h
index ece49aa..d11f9ae 100755
--- a/include/fastfields/impl/kernels/posdef.h
+++ b/include/fastfields/impl/kernels/posdef.h
@@ -1 +1,2 @@
+#pragma once
 #include "posdef/posdef.h"
diff --git a/include/fastfields/impl/kernels/posdef/cholesky.h b/include/fastfields/impl/kernels/posdef/cholesky.h
index f3a7eff..311cedb 100755
--- a/include/fastfields/impl/kernels/posdef/cholesky.h
+++ b/include/fastfields/impl/kernels/posdef/cholesky.h
@@ -1,5 +1,4 @@
-#ifndef FF_POSDEF_CHOLESKY
-#define FF_POSDEF_CHOLESKY
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "../utils.h"
 #include "utils.h"
@@ -138,5 +137,3 @@ struct cholesky<offset_t, -1> {
 FF_NAMESPACE_END(posdef)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_POSDEF_CHOLESKY
diff --git a/include/fastfields/impl/kernels/posdef/diag.inl b/include/fastfields/impl/kernels/posdef/diag.inl
index 2be755a..797046e 100755
--- a/include/fastfields/impl/kernels/posdef/diag.inl
+++ b/include/fastfields/impl/kernels/posdef/diag.inl
@@ -1,7 +1,4 @@
-#ifndef FF_POSDEF_DIAG
-#define FF_POSDEF_DIAG
-
-
+#pragma once
 template <typename offset_t, int C>
 struct utils<type::Diag, offset_t, C>: public common_diag<offset_t, C>
 {
@@ -221,5 +218,3 @@ struct utils<type::Diag, offset_t, -1>: public common_diag<offset_t, -1>
             internal::div<reduce_t>(o[c], 1., h[c]);
     }
 };
-
-#endif // FF_POSDEF_DIAG
diff --git a/include/fastfields/impl/kernels/posdef/estatics.inl b/include/fastfields/impl/kernels/posdef/estatics.inl
index 36496ee..64c1ea4 100755
--- a/include/fastfields/impl/kernels/posdef/estatics.inl
+++ b/include/fastfields/impl/kernels/posdef/estatics.inl
@@ -1,6 +1,4 @@
-#ifndef FF_POSDEF_ESTATICS
-#define FF_POSDEF_ESTATICS
-
+#pragma once
 template <typename offset_t, int C>
 struct utils<type::ESTATICS, offset_t, C>: public common_estatics<offset_t, C>
 {
@@ -204,5 +202,3 @@ struct utils<type::ESTATICS, offset_t, -1>: public common_estatics<offset_t, -1>
         }
     }
 };
-
-#endif  // FF_POSDEF_ESTATICS
diff --git a/include/fastfields/impl/kernels/posdef/eye.inl b/include/fastfields/impl/kernels/posdef/eye.inl
index 385932a..0710202 100755
--- a/include/fastfields/impl/kernels/posdef/eye.inl
+++ b/include/fastfields/impl/kernels/posdef/eye.inl
@@ -1,6 +1,4 @@
-#ifndef FF_POSDEF_EYE
-#define FF_POSDEF_EYE
-
+#pragma once
 template <typename offset_t, int C>
 struct utils<type::Eye, offset_t, C>: public common_eye<offset_t, C>
 {
@@ -120,5 +118,3 @@ struct utils<type::Eye, offset_t, -1>: public common_eye<offset_t, -1>
         internal::div<reduce_t>(*o, 1., *h);
     }
 };
-
-#endif // FF_POSDEF_EYE
diff --git a/include/fastfields/impl/kernels/posdef/full.inl b/include/fastfields/impl/kernels/posdef/full.inl
index fd6f31a..f9df8dd 100755
--- a/include/fastfields/impl/kernels/posdef/full.inl
+++ b/include/fastfields/impl/kernels/posdef/full.inl
@@ -1,6 +1,4 @@
-#ifndef FF_POSDEF_FULL
-#define FF_POSDEF_FULL
-
+#pragma once
 template <typename offset_t, int C>
 struct utils<type::Full, offset_t, C>: public common_sym<offset_t, C>
 {
@@ -130,5 +128,3 @@ struct utils<type::Full, offset_t, -1>: public common_sym<offset_t, -1>
         cholesky<offset_t>::solve_(C, b, v, static_cast<reduce_t>(0));   // solve linear system inplace
     }
 };
-
-#endif // FF_POSDEF_FULL
diff --git a/include/fastfields/impl/kernels/posdef/posdef.h b/include/fastfields/impl/kernels/posdef/posdef.h
index 62e0dfa..aebde8c 100755
--- a/include/fastfields/impl/kernels/posdef/posdef.h
+++ b/include/fastfields/impl/kernels/posdef/posdef.h
@@ -1,5 +1,4 @@
-#ifndef FF_POSDEF
-#define FF_POSDEF
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "../utils.h"
 #include "utils.h"
@@ -1009,5 +1008,3 @@ struct utils<type::None, offset_t, -1>: public common_none<offset_t, -1>
 FF_NAMESPACE_END(posdef)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_POSDEF
diff --git a/include/fastfields/impl/kernels/posdef/sym.inl b/include/fastfields/impl/kernels/posdef/sym.inl
index f59c02c..13e2c08 100755
--- a/include/fastfields/impl/kernels/posdef/sym.inl
+++ b/include/fastfields/impl/kernels/posdef/sym.inl
@@ -1,6 +1,4 @@
-#ifndef FF_POSDEF_SYM
-#define FF_POSDEF_SYM
-
+#pragma once
 // ---------------------------------------
 // Generic implementation with static size
 // ---------------------------------------
@@ -1089,5 +1087,3 @@ struct utils<type::Sym, offset_t, 1>: public common_sym<offset_t, 1>
        internal::set(o[0], i[0]);
     }
 };
-
-#endif // FF_POSDEF_SYM
diff --git a/include/fastfields/impl/kernels/posdef/utils.h b/include/fastfields/impl/kernels/posdef/utils.h
index 0788372..f0a2a9a 100755
--- a/include/fastfields/impl/kernels/posdef/utils.h
+++ b/include/fastfields/impl/kernels/posdef/utils.h
@@ -1,5 +1,4 @@
-#ifndef FF_POSDEF_UTILS
-#define FF_POSDEF_UTILS
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "../utils.h"
 
@@ -445,5 +444,3 @@ FF_NAMESPACE_END(internal)
 FF_NAMESPACE_END(posdef)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_POSDEF_UTILS
diff --git a/include/fastfields/impl/kernels/pushpull.h b/include/fastfields/impl/kernels/pushpull.h
index 4f16a5a..9a50422 100755
--- a/include/fastfields/impl/kernels/pushpull.h
+++ b/include/fastfields/impl/kernels/pushpull.h
@@ -1,3 +1,4 @@
+#pragma once
 #include "pushpull/1d.h"
 #include "pushpull/2d.h"
 #include "pushpull/3d.h"
diff --git a/include/fastfields/impl/kernels/pushpull/1d.h b/include/fastfields/impl/kernels/pushpull/1d.h
index e4d7e6f..f81b677 100755
--- a/include/fastfields/impl/kernels/pushpull/1d.h
+++ b/include/fastfields/impl/kernels/pushpull/1d.h
@@ -1,10 +1,9 @@
+#pragma once
 /***********************************************************************
  *
  *                                  1D
  *
  **********************************************************************/
-#ifndef FF_PUSHPULL_1D
-#define FF_PUSHPULL_1D
 #include <fastfields/core/cuda_switch.h>
 #include "../spline.h"
 #include "../bounds.h"
@@ -1578,5 +1577,3 @@ struct Kernels<Config<one, Spline<I>, Bound<B>, ABS>> {
 FF_NAMESPACE_END(pushpull)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_PUSHPULL_1D
diff --git a/include/fastfields/impl/kernels/pushpull/2d.h b/include/fastfields/impl/kernels/pushpull/2d.h
index a9e81a7..8310391 100755
--- a/include/fastfields/impl/kernels/pushpull/2d.h
+++ b/include/fastfields/impl/kernels/pushpull/2d.h
@@ -1,10 +1,9 @@
+#pragma once
 /***********************************************************************
  *
  *                                  2D
  *
  **********************************************************************/
-#ifndef FF_PUSHPULL_2D
-#define FF_PUSHPULL_2D
 #include <fastfields/core/cuda_switch.h>
 #include "../spline.h"
 #include "../bounds.h"
@@ -1252,5 +1251,3 @@ struct Kernels<Config<two, Spline<IX,IY>, Bound<BX, BY>, ABS>> {
 FF_NAMESPACE_END(pushpull)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_PUSHPULL_2D
diff --git a/include/fastfields/impl/kernels/pushpull/3d.h b/include/fastfields/impl/kernels/pushpull/3d.h
index 9b01dfe..9c2624c 100755
--- a/include/fastfields/impl/kernels/pushpull/3d.h
+++ b/include/fastfields/impl/kernels/pushpull/3d.h
@@ -1,10 +1,9 @@
+#pragma once
 /***********************************************************************
  *
  *                                  3D
  *
  **********************************************************************/
-#ifndef FF_PUSHPULL_3D
-#define FF_PUSHPULL_3D
 #include <fastfields/core/cuda_switch.h>
 #include "../spline.h"
 #include "../bounds.h"
@@ -1848,5 +1847,3 @@ struct Kernels<Config<three, Spline<IX,IY,IZ>, Bound<BX,BY,BZ>, ABS>> {
 FF_NAMESPACE_END(pushpull)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_PUSHPULL_3D
diff --git a/include/fastfields/impl/kernels/pushpull/nd.h b/include/fastfields/impl/kernels/pushpull/nd.h
index 03df18a..12c2d27 100755
--- a/include/fastfields/impl/kernels/pushpull/nd.h
+++ b/include/fastfields/impl/kernels/pushpull/nd.h
@@ -1,10 +1,9 @@
+#pragma once
 /***********************************************************************
  *
  *                                  ND
  *
  **********************************************************************/
-#ifndef FF_PUSHPULL_ND
-#define FF_PUSHPULL_ND
 #include <fastfields/core/cuda_switch.h>
 #include "../spline.h"
 #include "../bounds.h"
@@ -485,5 +484,3 @@ struct Kernels<PushPullConfig<D,Spline<>,Bound<>,ABS>> {
 FF_NAMESPACE_END(pushpull)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif FF_PUSHPULL_ND
diff --git a/include/fastfields/impl/kernels/pushpull/utils.h b/include/fastfields/impl/kernels/pushpull/utils.h
index 6d3e67c..94b62a5 100755
--- a/include/fastfields/impl/kernels/pushpull/utils.h
+++ b/include/fastfields/impl/kernels/pushpull/utils.h
@@ -1,5 +1,4 @@
-#ifndef FF_PUSHPULL_UTILS
-#define FF_PUSHPULL_UTILS
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "../spline.h"
 #include "../bounds.h"
@@ -1026,5 +1025,3 @@ struct PushPullUtils<C,B,ABS> {
 FF_NAMESPACE_END(pushpull)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_PUSHPULL_UTILS
diff --git a/include/fastfields/impl/kernels/regularisers.h b/include/fastfields/impl/kernels/regularisers.h
index 29562ff..9cf2450 100755
--- a/include/fastfields/impl/kernels/regularisers.h
+++ b/include/fastfields/impl/kernels/regularisers.h
@@ -1,2 +1,3 @@
+#pragma once
 #include "regularisers/flow.h"
 #include "regularisers/field.h"
diff --git a/include/fastfields/impl/kernels/regularisers/field.h b/include/fastfields/impl/kernels/regularisers/field.h
index 6185513..b2a3a42 100755
--- a/include/fastfields/impl/kernels/regularisers/field.h
+++ b/include/fastfields/impl/kernels/regularisers/field.h
@@ -1,3 +1,4 @@
+#pragma once
 #include "field/1d.h"
 #include "field/2d.h"
 #include "field/3d.h"
diff --git a/include/fastfields/impl/kernels/regularisers/field/1d.h b/include/fastfields/impl/kernels/regularisers/field/1d.h
index 625e419..2992037 100755
--- a/include/fastfields/impl/kernels/regularisers/field/1d.h
+++ b/include/fastfields/impl/kernels/regularisers/field/1d.h
@@ -1,5 +1,4 @@
-#ifndef FF_REGULARISERS_FIELD_1D
-#define FF_REGULARISERS_FIELD_1D
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "../../bounds.h"
 #include "../../utils.h"
@@ -1129,5 +1128,3 @@ struct Kernels<Config<one, _C, T...>>
 FF_NAMESPACE_END(reg_field)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_REGULARISERS_FIELD_1D
diff --git a/include/fastfields/impl/kernels/regularisers/field/2d.h b/include/fastfields/impl/kernels/regularisers/field/2d.h
index 1f307ea..060e0b9 100755
--- a/include/fastfields/impl/kernels/regularisers/field/2d.h
+++ b/include/fastfields/impl/kernels/regularisers/field/2d.h
@@ -1,5 +1,4 @@
-#ifndef FF_REGULARISERS_FIELD_2D
-#define FF_REGULARISERS_FIELD_2D
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "../../bounds.h"
 #include "../../utils.h"
@@ -1425,6 +1424,3 @@ struct Kernels<Config<two, _C, T...>>
 FF_NAMESPACE_END(reg_field)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-
-#endif // FF_REGULARISERS_FIELD_2D
diff --git a/include/fastfields/impl/kernels/regularisers/field/3d.h b/include/fastfields/impl/kernels/regularisers/field/3d.h
index 083a44d..05bf443 100755
--- a/include/fastfields/impl/kernels/regularisers/field/3d.h
+++ b/include/fastfields/impl/kernels/regularisers/field/3d.h
@@ -1,5 +1,4 @@
-#ifndef FF_REGULARISERS_FIELD_3D
-#define FF_REGULARISERS_FIELD_3D
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "../../bounds.h"
 #include "../../utils.h"
@@ -1753,5 +1752,3 @@ struct Kernels<Config<three, _C, T...>>
 FF_NAMESPACE_END(reg_field)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_REGULARISERS_FIELD_3D
diff --git a/include/fastfields/impl/kernels/regularisers/field/utils.h b/include/fastfields/impl/kernels/regularisers/field/utils.h
index 14e7c2a..f129ec3 100755
--- a/include/fastfields/impl/kernels/regularisers/field/utils.h
+++ b/include/fastfields/impl/kernels/regularisers/field/utils.h
@@ -1,5 +1,4 @@
-#ifndef FF_REGULARISERS_UTILS
-#define FF_REGULARISERS_UTILS
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "../../bounds.h"
 #include "../../utils.h"
@@ -156,5 +155,3 @@ bool patch3(const offset_t loc[N], offset_t n)
 FF_NAMESPACE_END(reg_field)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_REGULARISERS_UTILS
diff --git a/include/fastfields/impl/kernels/regularisers/flow.h b/include/fastfields/impl/kernels/regularisers/flow.h
index d38918c..e8d0c85 100755
--- a/include/fastfields/impl/kernels/regularisers/flow.h
+++ b/include/fastfields/impl/kernels/regularisers/flow.h
@@ -1,3 +1,4 @@
+#pragma once
 #include "flow/1d.h"
 #include "flow/2d.h"
 #include "flow/3d.h"
diff --git a/include/fastfields/impl/kernels/regularisers/flow/1d.h b/include/fastfields/impl/kernels/regularisers/flow/1d.h
index 388b988..bf7db4d 100755
--- a/include/fastfields/impl/kernels/regularisers/flow/1d.h
+++ b/include/fastfields/impl/kernels/regularisers/flow/1d.h
@@ -1,5 +1,4 @@
-#ifndef FF_REGULARISERS_FLOW_1D
-#define FF_REGULARISERS_FLOW_1D
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "../../bounds.h"
 #include "../../utils.h"
@@ -847,5 +846,3 @@ struct RegFlow<one, scalar_t, reduce_t, offset_t, BX> {
 FF_NAMESPACE_END(reg_flow)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_REGULARISERS_FLOW_1D
diff --git a/include/fastfields/impl/kernels/regularisers/flow/2d.h b/include/fastfields/impl/kernels/regularisers/flow/2d.h
index 1af7a05..f83e886 100755
--- a/include/fastfields/impl/kernels/regularisers/flow/2d.h
+++ b/include/fastfields/impl/kernels/regularisers/flow/2d.h
@@ -1,5 +1,4 @@
-#ifndef FF_REGULARISERS_FLOW_2D
-#define FF_REGULARISERS_FLOW_2D
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "../../bounds.h"
 #include "../../utils.h"
@@ -1647,5 +1646,3 @@ struct RegFlow<two, scalar_t, reduce_t, offset_t, BX, BY> {
 FF_NAMESPACE_END(reg_flow)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_REGULARISERS_FLOW_2D
diff --git a/include/fastfields/impl/kernels/regularisers/flow/3d.h b/include/fastfields/impl/kernels/regularisers/flow/3d.h
index 9fc6159..350d52c 100755
--- a/include/fastfields/impl/kernels/regularisers/flow/3d.h
+++ b/include/fastfields/impl/kernels/regularisers/flow/3d.h
@@ -1,5 +1,4 @@
-#ifndef FF_REGULARISERS_FLOW_3D
-#define FF_REGULARISERS_FLOW_3D
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "../../bounds.h"
 #include "../../utils.h"
@@ -2100,5 +2099,3 @@ struct RegFlow<three, scalar_t, reduce_t, offset_t, BX, BY, BZ> {
 FF_NAMESPACE_END(reg_flow)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_REGULARISERS_FLOW_3D
diff --git a/include/fastfields/impl/kernels/regularisers/flow/utils.h b/include/fastfields/impl/kernels/regularisers/flow/utils.h
index 394b858..d6fdcaa 100755
--- a/include/fastfields/impl/kernels/regularisers/flow/utils.h
+++ b/include/fastfields/impl/kernels/regularisers/flow/utils.h
@@ -1,5 +1,4 @@
-#ifndef FF_REGULARISERS_FLOW_UTILS
-#define FF_REGULARISERS_FLOW_UTILS
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "../../bounds.h"
 #include "../../utils.h"
@@ -126,5 +125,3 @@ bool patch3(const offset_t loc[N], offset_t n)
 FF_NAMESPACE_END(reg_flow)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_REGULARISERS_FLOW_UTILS
diff --git a/include/fastfields/impl/kernels/resize.h b/include/fastfields/impl/kernels/resize.h
index 6162df7..6369dc7 100755
--- a/include/fastfields/impl/kernels/resize.h
+++ b/include/fastfields/impl/kernels/resize.h
@@ -1,5 +1,4 @@
-#ifndef FF_RESIZE
-#define FF_RESIZE
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "spline.h"
 #include "bounds.h"
@@ -973,5 +972,3 @@ struct Multiscale<three, IX, BX, IY, BY, IZ, BZ> {
 FF_NAMESPACE_END(resize)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_RESIZE
diff --git a/include/fastfields/impl/kernels/restrict.h b/include/fastfields/impl/kernels/restrict.h
index 10d6c49..b743c12 100755
--- a/include/fastfields/impl/kernels/restrict.h
+++ b/include/fastfields/impl/kernels/restrict.h
@@ -1,5 +1,4 @@
-#ifndef FF_RESTRICT
-#define FF_RESTRICT
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "spline.h"
 #include "bounds.h"
@@ -452,5 +451,3 @@ struct Multiscale<three, two, L> {
 FF_NAMESPACE_END(restrict)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_RESTRICT
diff --git a/include/fastfields/impl/kernels/splinc.h b/include/fastfields/impl/kernels/splinc.h
index b65e901..e9c9990 100755
--- a/include/fastfields/impl/kernels/splinc.h
+++ b/include/fastfields/impl/kernels/splinc.h
@@ -1,3 +1,4 @@
+#pragma once
 // Compute spline interpolating coefficients
 //
 // These functions are ported from the C routines in SPM's bsplines.c
@@ -24,8 +25,6 @@
 //        "Splines: A Perfect Fit for Signal and Image Processing,"
 //        IEEE Signal Processing Magazine 16(6):22-38 (1999).
 
-#ifndef FF_SPLINC
-#define FF_SPLINC
 #include <fastfields/core/cuda_switch.h>
 #include "spline.h"
 #include "bounds.h"
@@ -335,5 +334,3 @@ inline FF_CUDEV void filter(scalar_t * inp, offset_t size, offset_t stride,
 FF_NAMESPACE_END(splinc)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_SPLINC
diff --git a/include/fastfields/impl/kernels/spline.h b/include/fastfields/impl/kernels/spline.h
index 89d7364..6bb0241 100755
--- a/include/fastfields/impl/kernels/spline.h
+++ b/include/fastfields/impl/kernels/spline.h
@@ -1,3 +1,4 @@
+#pragma once
 // This file contains static functions for handling (0-7 order)
 // spline weights.
 // It also defines an enumerated types that encodes each boundary type.
@@ -23,8 +24,6 @@
 
 // TODO? other types of basis functions (gauss, sinc)
 
-#ifndef FF_SPLINE
-#define FF_SPLINE
 #include <fastfields/core/cuda_switch.h>
 #include "meta.h"
 
@@ -1443,5 +1442,3 @@ template <> struct dyn<type::Dynamic>
 FF_NAMESPACE_END(spline)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_SPLINE
diff --git a/include/fastfields/impl/kernels/tetrahedron.h b/include/fastfields/impl/kernels/tetrahedron.h
index ffd8f12..38375f2 100755
--- a/include/fastfields/impl/kernels/tetrahedron.h
+++ b/include/fastfields/impl/kernels/tetrahedron.h
@@ -1,5 +1,4 @@
-#ifndef FF_TETRAHEDRON
-#define FF_TETRAHEDRON
+#pragma once
 #include <fastfields/core/cuda_switch.h>
 #include "utils.h"
 
@@ -238,6 +237,3 @@ void pull1(scalar_t * output,
 FF_NAMESPACE_END(tetra)
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-
-#endif // FF_TETRAHEDRON
diff --git a/include/fastfields/impl/kernels/threadpool.h b/include/fastfields/impl/kernels/threadpool.h
index 4948eeb..833b168 100755
--- a/include/fastfields/impl/kernels/threadpool.h
+++ b/include/fastfields/impl/kernels/threadpool.h
@@ -1,9 +1,8 @@
+#pragma once
 // Copyright (c) Yasser Asmi
 // Released under the MIT License (http://opensource.org/licenses/MIT)
 // https://github.com/YasserAsmi/wstpool
 
-#ifndef FF_THREADPOOL_H
-#define FF_THREADPOOL_H
 
 #include <atomic>
 #include <list>
@@ -256,5 +255,3 @@ class ThreadPool
 FF_NAMESPACE_END(FF_NS)
 
 #include "threadpool.inl"
-
-#endif // FF_THREADPOOL_H
diff --git a/include/fastfields/impl/kernels/threadpool.inl b/include/fastfields/impl/kernels/threadpool.inl
index 3f3bc4a..8fbf945 100755
--- a/include/fastfields/impl/kernels/threadpool.inl
+++ b/include/fastfields/impl/kernels/threadpool.inl
@@ -1,5 +1,4 @@
-#ifndef FF_THREADPOOL_INL
-#define FF_THREADPOOL_INL
+#pragma once
 #include <memory>
 #include <string>
 #include <thread>
@@ -75,4 +74,3 @@ inline std::shared_ptr<ThreadPool> get_global_pool() {
 }
 
 FF_NAMESPACE_END(FF_NS)
-#endif // FF_THREADPOOL_INL
diff --git a/include/fastfields/impl/kernels/utils.h b/include/fastfields/impl/kernels/utils.h
index ab0cf7c..37394ce 100755
--- a/include/fastfields/impl/kernels/utils.h
+++ b/include/fastfields/impl/kernels/utils.h
@@ -1,5 +1,4 @@
-#ifndef FF_UTILS
-#define FF_UTILS
+#pragma once
 #include <limits>
 #include <fastfields/core/cuda_switch.h>
 
@@ -697,5 +696,3 @@ FF_CUHOST inline bool canUse32BitIndexMath(
 
 FF_NAMESPACE_END(FF_DEVICE)
 FF_NAMESPACE_END(FF_NS)
-
-#endif // FF_UTILS
diff --git a/include/fastfields/impl/kernels/vector/abstract_ptr.h b/include/fastfields/impl/kernels/vector/abstract_ptr.h
index 0fcf3a9..a4c9ce9 100755
--- a/include/fastfields/impl/kernels/vector/abstract_ptr.h
+++ b/include/fastfields/impl/kernels/vector/abstract_ptr.h
@@ -1,5 +1,4 @@
-#ifndef FF_VECTOR_ABSTRACTPTR_H
-#define FF_VECTOR_ABSTRACTPTR_H
+#pragma once
 #include <stdexcept>
 #include "forward.h"
 #include "traits.h"
@@ -438,5 +437,3 @@ using AbstractDynamicPointer = AbstractPointer<T, DynamicStride, D>;
 
 
 } // namespace ff
-
-#endif // FF_VECTOR_ABSTRACTPTR_H
diff --git a/include/fastfields/impl/kernels/vector/abstract_sized.h b/include/fastfields/impl/kernels/vector/abstract_sized.h
index e59d08b..2a88cf5 100755
--- a/include/fastfields/impl/kernels/vector/abstract_sized.h
+++ b/include/fastfields/impl/kernels/vector/abstract_sized.h
@@ -1,5 +1,4 @@
-#ifndef FF_VECTOR_ABSTRACTSIZED_H
-#define FF_VECTOR_ABSTRACTSIZED_H
+#pragma once
 #include <stdexcept>
 #include "forward.h"
 #include "abstract_ptr.h"
@@ -257,5 +256,3 @@ using AbstractDynamicSizedPointer = AbstractSizedPointer<T, DynamicSize, S, D>;
 
 
 } // namespace ff
-
-#endif // FF_VECTOR_ABSTRACTSIZED_H
diff --git a/include/fastfields/impl/kernels/vector/abstract_vector.h b/include/fastfields/impl/kernels/vector/abstract_vector.h
index 9e386b4..69b4c72 100755
--- a/include/fastfields/impl/kernels/vector/abstract_vector.h
+++ b/include/fastfields/impl/kernels/vector/abstract_vector.h
@@ -1,5 +1,4 @@
-#ifndef FF_VECTOR_ABTRACTVECTOR_H
-#define FF_VECTOR_ABTRACTVECTOR_H
+#pragma once
 #include "forward.h"
 #include "traits.h"
 #include "weak_sized.h"
@@ -700,7 +699,3 @@ struct std::tuple_element< I, ff::AbstractVector<T, N, S, D> >
 {
     using type = T;
 };
-
-
-
-#endif // FF_VECTOR_ABTRACTVECTOR_H
diff --git a/include/fastfields/impl/kernels/vector/concrete_vector.h b/include/fastfields/impl/kernels/vector/concrete_vector.h
index e20824c..0fc8dc7 100755
--- a/include/fastfields/impl/kernels/vector/concrete_vector.h
+++ b/include/fastfields/impl/kernels/vector/concrete_vector.h
@@ -1,5 +1,4 @@
-#ifndef FF_VECTOR_CONCRETEVECTOR_H
-#define FF_VECTOR_CONCRETEVECTOR_H
+#pragma once
 #include <initializer_list>
 #include "forward.h"
 #include "traits.h"
@@ -224,5 +223,3 @@ struct std::tuple_element< I, ff::Vector<T, N, D> >
 {
     using type = T;
 };
-
-#endif // FF_VECTOR_CONCRETEVECTOR_H
diff --git a/include/fastfields/impl/kernels/vector/forward.h b/include/fastfields/impl/kernels/vector/forward.h
index 84e5cb4..497883a 100755
--- a/include/fastfields/impl/kernels/vector/forward.h
+++ b/include/fastfields/impl/kernels/vector/forward.h
@@ -1,5 +1,4 @@
-#ifndef FF_VECTOR_FORWARD_H
-#define FF_VECTOR_FORWARD_H
+#pragma once
 #include <limits>
 
 namespace ff {
@@ -29,5 +28,3 @@ template <typename T, unsigned long N=DynamicSize, typename D=void>
 class Vector;
 
 }
-
-#endif // FF_VECTOR_FORWARD_H
diff --git a/include/fastfields/impl/kernels/vector/stream.h b/include/fastfields/impl/kernels/vector/stream.h
index 5fb185e..f825d10 100755
--- a/include/fastfields/impl/kernels/vector/stream.h
+++ b/include/fastfields/impl/kernels/vector/stream.h
@@ -1,5 +1,4 @@
-#ifndef FF_VECTOR_STREAM_H
-#define FF_VECTOR_STREAM_H
+#pragma once
 #include <iostream>
 #include "abstract_ptr.h"
 #include "abstract_sized.h"
@@ -134,5 +133,3 @@ std::ostream& operator <<(
 {
     return Vector_print(stream, ptr);
 }
-
-#endif // FF_VECTOR_STREAM_H
diff --git a/include/fastfields/impl/kernels/vector/traits.h b/include/fastfields/impl/kernels/vector/traits.h
index a75d96c..f24f098 100755
--- a/include/fastfields/impl/kernels/vector/traits.h
+++ b/include/fastfields/impl/kernels/vector/traits.h
@@ -1,6 +1,4 @@
-#ifndef FF_VECTOR_TRAITS_H
-#define FF_VECTOR_TRAITS_H
-
+#pragma once
 namespace ff {
 namespace internal {
 
@@ -62,5 +60,3 @@ struct guess_iterator<BaseType, void> {
 
 } // internal
 } // jf
-
-#endif // FF_VECTOR_TRAITS_H
diff --git a/include/fastfields/impl/kernels/vector/vector.h b/include/fastfields/impl/kernels/vector/vector.h
index 211c449..db1591d 100755
--- a/include/fastfields/impl/kernels/vector/vector.h
+++ b/include/fastfields/impl/kernels/vector/vector.h
@@ -1,6 +1,4 @@
-#ifndef FF_VECTOR_VECTOR_H
-#define FF_VECTOR_VECTOR_H
-
+#pragma once
 #include "weak_ref.h"
 #include "weak_sized.h"
 #include "weak_vector.h"
@@ -134,5 +132,3 @@ class Vector: AbstractVector
     begin(), cbegin(), rbegin(), crbegin(), end(), cend(), rend(), crend()
 };
 */
-
-#endif // FF_VECTOR_VECTOR_H
diff --git a/include/fastfields/impl/kernels/vector/weak_ref.h b/include/fastfields/impl/kernels/vector/weak_ref.h
index 3e2eac4..28d04b6 100755
--- a/include/fastfields/impl/kernels/vector/weak_ref.h
+++ b/include/fastfields/impl/kernels/vector/weak_ref.h
@@ -1,5 +1,4 @@
-#ifndef FF_VECTOR_WEAKREF_H
-#define FF_VECTOR_WEAKREF_H
+#pragma once
 #include "forward.h"
 #include "traits.h"
 #include "abstract_ptr.h"
@@ -92,5 +91,3 @@ WeakRef<T,S> weak_ref(const AbstractPointer<T,S,D> & ptr)
 
 
 } // namespace ff
-
-#endif // FF_VECTOR_WEAKREF_H
diff --git a/include/fastfields/impl/kernels/vector/weak_sized.h b/include/fastfields/impl/kernels/vector/weak_sized.h
index 226c87d..ed3df92 100755
--- a/include/fastfields/impl/kernels/vector/weak_sized.h
+++ b/include/fastfields/impl/kernels/vector/weak_sized.h
@@ -1,5 +1,4 @@
-#ifndef FF_VECTOR_WEAKSIZEDREF_H
-#define FF_VECTOR_WEAKSIZEDREF_H
+#pragma once
 #include "forward.h"
 #include "abstract_sized.h"
 #include <fastfields/core/cuda_switch.h>
@@ -135,5 +134,3 @@ WeakSizedRef<T,N,S> weak_ref(const AbstractSizedPointer<T,S,N,D> & ptr)
 
 
 } // namespace ff
-
-#endif // FF_VECTOR_WEAKSIZEDREF_H
diff --git a/include/fastfields/impl/kernels/vector/weak_vector.h b/include/fastfields/impl/kernels/vector/weak_vector.h
index c8d754b..a55a23a 100755
--- a/include/fastfields/impl/kernels/vector/weak_vector.h
+++ b/include/fastfields/impl/kernels/vector/weak_vector.h
@@ -1,5 +1,4 @@
-#ifndef FF_VECTOR_WEAKVECTOR_H
-#define FF_VECTOR_WEAKVECTOR_H
+#pragma once
 #include "forward.h"
 #include "traits.h"
 #include "abstract_vector.h"
@@ -138,5 +137,3 @@ struct std::tuple_element< I, ff::WeakVector<T, N, S, D> >
 {
     using type = T;
 };
-
-#endif // FF_VECTOR_WEAKVECTOR_H
diff --git a/tools/normalise-header-guards.py b/tools/normalise-header-guards.py
new file mode 100644
index 0000000..802f6e2
--- /dev/null
+++ b/tools/normalise-header-guards.py
@@ -0,0 +1,362 @@
+#!/usr/bin/env python3
+"""
+normalise-header-guards.py -- `#pragma once` in every header, one convention.
+
+THE RULE THIS APPLIES
+--------------------------------------------------------------------------
+Every header in this repository has `#pragma once` as its first line and
+carries no whole-file `#ifndef`/`#define`/`#endif` guard. Line 1, with no
+exception for a licence or provenance comment: "is line 1 `#pragma once`" is
+a rule that needs no judgement to apply and none to check, and it is what the
+headers already using the pragma did. Attribution comments keep their text
+and simply sit one line lower.
+
+The tree had drifted into four conventions at once -- 94 headers with a guard
+only, 12 with the pragma only, 5 with both, and 6 with neither -- split by
+which of the six pre-consolidation repositories a file came from rather than
+by any decision. `#pragma once` is now the single convention.
+
+`#pragma once` is not ISO C++, but every compiler this project targets or
+plans to target supports it: clang, g++, nvcc and MSVC. The historical hazard
+here -- that it keys on file identity, which was ambiguous when every
+cross-repo dependency was a symlink -- is gone: `main` has no `.gitmodules`,
+no gitlinks and no symlinks.
+
+VENDORED FILES KEEP THEIR UPSTREAM GUARDS
+--------------------------------------------------------------------------
+`include/fastfields/core/dlpack.h` is verbatim upstream code and is never
+touched. Its `DLPACK_DLPACK_H_` guard is the *upstream* macro, which is what
+lets our copy and a system DLPack header with the same guard collapse into a
+single inclusion -- something `#pragma once` cannot do for two distinct files.
+Replacing it would break that interoperation, so it stays. `--check` treats it
+as exempt but still reports it, and fails loudly if the path disappears (e.g.
+after a file move) rather than silently dropping the exemption.
+
+Six other headers carry third-party provenance, and all six are ADAPTATIONS
+rather than drop-in vendored copies, so the pragma applies to them:
+
+    impl/kernels/atomic.h            "CUDA portion copied from PyTorch/ATen"
+    impl/kernels/parallel.h          "adapted from PyTorch/ATen ParallelNative"
+    impl/kernels/parallel_impl.h     ditto
+    impl/kernels/threadpool.h        YasserAsmi/wstpool (MIT)
+    impl/kernels/threadpool.inl      "some of this is copied from pytorch/aten"
+    impl/cuda/utils.h                two helpers "(Copied from PyTorch)"
+    impl/kernels/distance/mesh.h     InteractiveComputerGraphics/TriangleMeshDistance
+
+The test that settles it is not how much text came from upstream, it is
+whether the file carries an upstream *guard macro* to interoperate with. None
+of them does: every one is guarded by a name this project invented (`FF_ATOMIC`,
+`FF_PARALLEL_H`, `FF_THREADPOOL_H`, ...), or -- in `impl/cuda/utils.h`'s case --
+by nothing at all, since it already used `#pragma once` before this sweep. They
+are also re-namespaced into `ff::` via `FF_NAMESPACE_BEGIN`, use this project's
+`FF_CUHOST`/`FF_CUDEV` qualifiers, and include project headers, so no upstream
+copy could substitute for them and none is on any include path. There is
+nothing for a guard to interoperate with, and `dlpack.h` remains the only
+vendored file. (Copyright notices are untouched either way -- this is about
+include mechanics, not attribution.)
+
+REMOVING A GUARD IS NOT AUTOMATICALLY INERT
+--------------------------------------------------------------------------
+A guard macro can be *tested* from outside the header that defines it. A
+`#ifdef` on a guard name somewhere else in the tree makes that `#define`
+load-bearing, and deleting it silently changes what compiles -- the one way
+a sweep like this can break something without any diagnostic. So the script
+does not assume: before removing anything it greps the whole repository for
+every guard macro, and refuses to run at all if one is mentioned in a
+compiled source outside its own header. `--check` runs the same audit, so a
+future header that starts testing a guard name turns the check red.
+
+Mentions outside compiled sources cannot affect what compiles, so they are
+reported rather than blocking.
+
+On the tree as of this commit the audit is clean: all 99 guard macros are
+referenced exactly once, by their own `#ifndef`, with no `#ifdef` on a guard
+name anywhere. The only mentions elsewhere are inert text in the frozen
+`tools/consolidate.sh` (which quotes header text it generated), one prose
+line in `MIGRATION-PROVENANCE.md`, and this script's own docstring.
+
+WHAT IS NOT A HEADER GUARD, AND SURVIVES
+--------------------------------------------------------------------------
+Only a guard that brackets the *whole file* is removed. `#ifndef` blocks that
+guard part of a file, or that exist to make a definition idempotent across
+several files, are untouched. Two families matter here:
+
+  * `FF_LIB_BOUND_SPLINE_T` -- eight `api/*.h` headers each wrap the shared
+    `bound_t`/`spline_t` declarations in it so they can be co-included. This
+    is exactly the job `#pragma once` cannot do (one macro, eight files), and
+    it is depended on downstream: `fastfields-dlpack/src/ext.cpp` includes all
+    eight and says so in a comment.
+  * `FF_POSDEF_MAX_NBATCH`, `FF_PP_MAX_NBATCH`, `FF_RESIZE_MAX_NBATCH`,
+    `FF_RESTRICT_MAX_NBATCH`, `FF_SPLINC_MAX_NBATCH`, `FF_AUTOCAST_PINNED_HOST`
+    -- `#ifndef X / #define X <value>` overridable build knobs.
+
+The guard finder only accepts an `#ifndef` that is the file's first directive,
+whose `#define` has an empty replacement list, and whose `#endif` is the file's
+last directive, so none of the above can be mistaken for a guard.
+
+USAGE
+--------------------------------------------------------------------------
+    python3 tools/normalise-header-guards.py           # apply
+    python3 tools/normalise-header-guards.py --check   # verify, change nothing
+
+Idempotent and deterministic: re-running over a normalised tree rewrites
+nothing, and running over the pre-sweep tree reproduces the sweep exactly.
+
+If this lands on a base that has moved, do NOT resolve conflicts by hand:
+reset, re-run the script on the new base, and commit that.
+"""
+
+import os
+import re
+import sys
+
+ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+
+SOURCE_DIRS = ("include", "src", "tests")
+HEADER_EXTS = (".h", ".hpp", ".inl", ".cuh")
+COMPILED_EXTS = HEADER_EXTS + (".cpp", ".cu")
+
+# Verbatim third-party code: never rewritten, keeps its upstream guard.
+VENDORED = {"include/fastfields/core/dlpack.h"}
+
+
+def headers():
+    for d in SOURCE_DIRS:
+        for dirpath, _, filenames in os.walk(os.path.join(ROOT, d)):
+            for name in sorted(filenames):
+                if name.endswith(HEADER_EXTS):
+                    yield os.path.relpath(os.path.join(dirpath, name), ROOT)
+
+
+def repo_files():
+    for dirpath, dirnames, filenames in os.walk(ROOT):
+        dirnames[:] = [d for d in dirnames if d not in (".git", "build")]
+        for name in sorted(filenames):
+            yield os.path.relpath(os.path.join(dirpath, name), ROOT)
+
+
+def read(rel):
+    with open(os.path.join(ROOT, rel), encoding="utf-8", errors="ignore") as fh:
+        return fh.read()
+
+
+def strip_comments(text):
+    """Blank out comments so directive scanning cannot be fooled by an
+    `#endif` inside one. Line structure is preserved."""
+    out, i, n = [], 0, len(text)
+    while i < n:
+        if text.startswith("/*", i):
+            j = text.find("*/", i + 2)
+            j = n if j < 0 else j + 2
+            out.append("".join(c if c == "\n" else " " for c in text[i:j]))
+            i = j
+        elif text.startswith("//", i):
+            j = text.find("\n", i)
+            j = n if j < 0 else j
+            out.append(" " * (j - i))
+            i = j
+        else:
+            out.append(text[i])
+            i += 1
+    return "".join(out)
+
+
+def directives(text):
+    """(line index, directive, rest) for every preprocessor directive, with
+    line continuations respected and comments already blanked."""
+    lines = strip_comments(text).split("\n")
+    out, i = [], 0
+    while i < len(lines):
+        m = re.match(r"\s*#\s*(\w+)\s*(.*)$", lines[i])
+        start = i
+        while lines[i].rstrip().endswith("\\") and i + 1 < len(lines):
+            i += 1
+        if m:
+            out.append((start, m.group(1), m.group(2).strip()))
+        i += 1
+    return out
+
+
+def find_guard(text):
+    """(name, ifndef line, define line, endif line) for a whole-file guard, or
+    None.
+
+    Requires the first directive to be `#ifndef N`, the second to be
+    `#define N` with an empty replacement list, and the conditional nesting
+    that `#ifndef` opens to close only at the file's last directive -- so a
+    partial-file `#ifndef`, or a `#define N <value>` build knob, is never
+    mistaken for a guard. A leading `#pragma once` is stepped over."""
+    ds = [d for d in directives(text) if d[1] != "pragma"]
+    if len(ds) < 3 or ds[0][1] != "ifndef":
+        return None
+    name = ds[0][2]
+    if not re.fullmatch(r"\w+", name or ""):
+        return None
+    if ds[1][1] != "define" or ds[1][2] != name:
+        return None
+    depth = 0
+    for k, (line, d, _rest) in enumerate(ds):
+        if d in ("if", "ifdef", "ifndef"):
+            depth += 1
+        elif d == "endif":
+            depth -= 1
+            if depth == 0:
+                if k != len(ds) - 1:
+                    return None
+                return name, ds[0][0], ds[1][0], line
+    return None
+
+
+def external_references(names):
+    """Every mention of a guard macro outside the header that defines it,
+    split into (blocking, inert).
+
+    Blocking = a mention in a compiled source, where it could be a `#ifdef`
+    that the guard's `#define` is load-bearing for. Inert = a mention anywhere
+    else (a script that quotes header text, a prose line in a doc, this
+    script's own docstring), which cannot affect what compiles but is still
+    reported so nobody has to wonder."""
+    owners = {name: rel for name, (rel, _) in names.items()}
+    pats = {n: re.compile(r"(?<![A-Za-z0-9_])%s(?![A-Za-z0-9_])" % re.escape(n))
+            for n in names}
+    blocking, inert = {}, {}
+    for rel in repo_files():
+        try:
+            text = read(rel)
+        except OSError:
+            continue
+        compiled = rel.startswith(SOURCE_DIRS) and rel.endswith(COMPILED_EXTS)
+        for name, pat in pats.items():
+            if owners[name] == rel or name not in text:
+                continue
+            for n, line in enumerate(text.split("\n"), 1):
+                if pat.search(line):
+                    bucket = blocking if compiled else inert
+                    bucket.setdefault(name, []).append((rel, n, line.strip()[:90]))
+    return blocking, inert
+
+
+def guarded_headers():
+    """{guard name: (rel, guard tuple)} for every non-vendored header that has
+    a whole-file guard."""
+    out = {}
+    for rel in headers():
+        if rel in VENDORED:
+            continue
+        g = find_guard(read(rel))
+        if g:
+            out[g[0]] = (rel, g)
+    return out
+
+
+def normalise(text):
+    lines = text.split("\n")
+    while lines and lines[-1] == "":
+        lines.pop()
+
+    g = find_guard(text)
+    drop = set()
+    if g:
+        _name, ifndef_at, define_at, endif_at = g
+        drop |= {ifndef_at, define_at, endif_at}
+    for i, line in enumerate(lines):
+        if re.match(r"\s*#\s*pragma\s+once\s*$", line):
+            drop.add(i)
+    lines = [l for i, l in enumerate(lines) if i not in drop]
+
+    # A guard's `#define` was often followed by a blank line, and its `#endif`
+    # preceded by one; drop what that leaves dangling rather than keeping a
+    # gap where a directive used to be.
+    while lines and not lines[-1].strip():
+        lines.pop()
+    while lines and not lines[0].strip():
+        lines.pop(0)
+
+    lines.insert(0, "#pragma once")
+    return "\n".join(lines) + "\n"
+
+
+def apply(check_only=False):
+    guarded = guarded_headers()
+    blocking, inert = external_references(guarded)
+    if blocking:
+        print("REFUSING TO REMOVE -- guard macro used in a compiled source:")
+        for name in sorted(blocking):
+            print("  %s (defined in %s)" % (name, guarded[name][0]))
+            for rel, n, line in blocking[name]:
+                print("      %s:%d: %s" % (rel, n, line))
+        return -1
+    if inert:
+        print("guard macros mentioned outside compiled sources (inert):")
+        for name in sorted(inert):
+            for rel, n, line in inert[name]:
+                print("  %s at %s:%d: %s" % (name, rel, n, line))
+
+    changed = 0
+    for rel in headers():
+        if rel in VENDORED:
+            continue
+        path = os.path.join(ROOT, rel)
+        original = read(rel)
+        text = normalise(original)
+        if text != original:
+            changed += 1
+            if check_only:
+                print("would rewrite %s" % rel)
+            else:
+                with open(path, "w", encoding="utf-8") as fh:
+                    fh.write(text)
+    print("%d header(s)%s" % (changed, " would change" if check_only else " rewritten"))
+    return changed
+
+
+def violations():
+    """Every header that does not satisfy the convention. Must be empty."""
+    hits = []
+
+    for rel in sorted(VENDORED):
+        if not os.path.isfile(os.path.join(ROOT, rel)):
+            hits.append(
+                "%s: listed as vendored but missing -- if it moved, update "
+                "VENDORED, do not drop the exemption" % rel
+            )
+
+    for rel in headers():
+        text = read(rel)
+        if rel in VENDORED:
+            if find_guard(text) is None:
+                hits.append("%s: vendored file lost its upstream guard" % rel)
+            continue
+
+        g = find_guard(text)
+        if g:
+            hits.append("%s: still has a whole-file guard (%s)" % (rel, g[0]))
+
+        if text.split("\n", 1)[0].strip() != "#pragma once":
+            hits.append("%s: first line is not #pragma once" % rel)
+        if sum(1 for d in directives(text)
+               if d[1] == "pragma" and d[2] == "once") != 1:
+            hits.append("%s: not exactly one #pragma once" % rel)
+
+    blocking, _inert = external_references(guarded_headers())
+    for name in sorted(blocking):
+        for rel, n, line in blocking[name]:
+            hits.append("guard %s used at %s:%d: %s" % (name, rel, n, line))
+    return hits
+
+
+if __name__ == "__main__":
+    check = "--check" in sys.argv
+    if apply(check_only=check) < 0:
+        sys.exit(1)
+    left = violations()
+    if left:
+        print("\nHEADERS NOT MATCHING THE CONVENTION:")
+        for h in left:
+            print("  " + h)
+    else:
+        print(
+            "\nevery header opens with #pragma once and carries no whole-file "
+            "guard; %s keeps its upstream guard." % ", ".join(sorted(VENDORED))
+        )
+    sys.exit(1 if left else 0)