DIY is a block-parallel library for implementing scalable algorithms that can execute both in-core and out-of-core. The same program can be executed with one or more threads per MPI process, seamlessly combining distributed-memory message passing with shared-memory thread parallelism. The abstraction enabling these capabilities is block parallelism; blocks and their message queues are mapped onto processing elements (MPI processes or threads) and are migrated between memory and storage by the DIY runtime. Complex communication patterns, including neighbor exchange, merge reduction, swap reduction, and all-to-all exchange, are possible in- and out-of-core in DIY.
DIY is released as open source software under a BSD style license.
DIY requires an MPI installation. We recommend MPICH.
You can clone this repository, or
You can download the latest tarball.
DIY is a header-only library. It does not need to be built; you can simply
include it in your project. The examples can be built using cmake from the
top level directory.
A simple DIY program, shown below, consists of the following components:
structs called blocks,- a diy object called the
master, - a set of callback functions performed on each block by
master.foreach(), - optionally one or more message exchanges between the blocks by
master.exchange(), and - there may be other collectives and global reductions not shown below.
The callback functions (enqueue_block() and average() in the example below) are given the block
pointer and a communication proxy for the message exchange between blocks. It is usual for the
callback functions to enqueue or dequeue messages from the proxy, so that information can be
received and sent during rounds of message exchange.
// --- main program --- //structBlock { float local, average; }; // define your block structure
Master master(world); // world = MPI_Comm
... // populate master with blocks
master.foreach<Block>(&enqueue_local); // call enqueue_local() for each block
master.exchange(); // exchange enqueued data between blocks
master.foreach<Block>(&average); // call average() for each block// --- callback functions --- //// enqueue block data prior to exchanging itvoidenqueue_local(Block* b, // one blockconst Proxy& cp, // communication proxy// i.e., the neighbor blocks with which// this block communicatesvoid* aux) // user-defined additional arguments
{
for (size_t i = 0; i < cp.link()->size(); i++) // for all neighbor blocks
cp.enqueue(cp.link()->target(i), b->local); // enqueue the data to be sent// to this neighbor block in the next// exchange
}
// use the received data after exchanging it, in this case compute its averagevoidaverage(Block* b, // one blockconst Proxy& cp, // communication proxy// i.e., the neighbor blocks with which// this block communicatesvoid* aux) // user-defined additional arguments
{
float x, average = 0;
for (size_t i = 0; i < cp.link()->size(); i++) // for all neighbor blocks
{
cp.dequeue(cp.link()->target(i).gid, x); // dequeue the data received from this// neighbor block in the last exchange
average += x;
}
b->average = average / cp.link()->size();
}