Optimized, immutable Java implementations of fixed-width, unsigned integers.
Currently 128 bit
(UInt128) and 256
bit (UInt256)
variants are available (with identical, BigInteger-style interfaces). It'd be
trivial to offer differently sized integers with the same semantics, as all
operations are implemented statically in terms of arrays.
juint requires Java 8.
Ignoring constant overhead, per-instance memory consumption is identical to
BigInteger's best case - i.e. an array holding the minimum number of integers
required to represent a given number - never zero prefixed.
Operation throughput is expected to be significantly higher than OpenJDK's
BigInteger for most operations (often dramatically so). There are exhaustive
(around 170) JMH micro-benchmarks per operation & magnitude in the bench
subproject.
and some updated 2023 benchmarks:
Each operation's bar represents the average throughput across all of its
magnitude-specific benchmark cases, relative to identical benchmarks which
operate on BigInteger. Typically, in the case of UInt256, there'd be
separate cases for one word, two words, four words (half) and 8 words (full),
each operating on a range of similarly wide values.
Erring on the side of fairness, the BigInteger reference benchmarks only
include the cost of constraining the result within the maximum width if the
operation will definitely overflow. As this approach requires a degree of
foreknowledge present in few real-life use cases, relative throughput
may be significantly improved from that depicted.
The multiply disparity above is due to HotSpot's intrinsification of
BigInteger.multiplyToLen, a private method used by BigInteger.multiply (and
pow, by association) - obviously not an optimization strategy available to
library code.
Like OpenJDK itself, juint is distributed under the terms of the GNU General
Public License (version 2) with the classpath exception:
...The copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules...
Please see the accompanying LICENSE file for details.
As mentioned, juint offers an interface compatible with BigInteger, and
follows a similar strategy to OpenJDK for division and the (String, int)
constructor. While I don't consider it a derived work, I don't want to have
to explain that to Gavin Belson in a courtroom.
Despite a strong personal preference for Public Domain software, retaining OpenJDK's license seems the prudent choice, and doesn't place additional burden on those consuming this project.