perf: copy optimization

[jodavies]

Here is an optimisation experiment, replacing all NCOPY/WCOPY macros with memmove (we can't be sure that memory regions never overlap in use of the macro for memcpy). The replacement alone is a negligible performance improvement (tentatively 1%?) but it is hard to detect within the usual run-to-run variation.

The followup commits improve some existing copies within the code by using the macros instead, and moving some conditionals outside of the copies. I identified the expensive copies with a profiler running the Forcer benchmark.

On my system (Ryzen 7900X, Ubuntu 24.04, GCC 13.3.0, tform -w12,), the results for the usual benchmarks are as follows:

Benchmark	Speedup w.r.t. v5.0.0
chromatic	1.05 ± 0.01
color	1.01 ± 0.01
fmft	1.03 ± 0.01
forcer	1.07 ± 0.00
forcer-exp	1.08 ± 0.01
mass-fact	1.00 ± 0.05
mbox1l	1.01 ± 0.02
minceex	1.07 ± 0.02
mincer	1.00 ± 0.05
sort-disk	0.98 ± 0.02
sort-large	0.99 ± 0.01
sort-small	1.01 ± 0.01
trace	1.02 ± 0.01

[vermaseren]

I think that most of the gain comes from copies with very many words, while the smaller copies give a loss. memcpy has to perform some tests, and hence has an overhead. I looked into this with Jan Kuipers because he liked memcpy but we had to find a number of bad bugs because of overwriting, and because of that we had to study those routines.

…

On 14 Feb 2026, at 14:20, jodavies ***@***.***> wrote: Here is an optimisation experiment, replacing all NCOPY/WCOPY macros with memmove (we can't be sure that memory regions never overlap in use of the macro for memcpy). The replacement alone is a negligible performance improvement (tentatively 1%?) but it is hard to detect within the usual run-to-run variation. The followup commits improve some existing copies within the code by using the macros instead, and moving some conditionals outside of the copies. I identified the expensive copies with a profiler running the Forcer benchmark. On my system (Ryzen 7900X, Ubuntu 24.04, GCC 13.3.0, tform -w12,), the results for the usual benchmarks are as follows: Benchmark Speedup w.r.t. v5.0.0 chromatic 1.05 ± 0.01 color 1.01 ± 0.01 fmft 1.03 ± 0.01 forcer 1.07 ± 0.00 forcer-exp 1.08 ± 0.01 mass-fact 1.00 ± 0.05 mbox1l 1.01 ± 0.02 minceex 1.07 ± 0.02 mincer 1.00 ± 0.05 sort-disk 0.98 ± 0.02 sort-large 0.99 ± 0.01 sort-small 1.01 ± 0.01 trace 1.02 ± 0.01 You can view, comment on, or merge this pull request online at: #799 Commit Summary d2e8ae4 <d2e8ae4> perf: use memmove for all NCOPY/WCOPY macros 2442e58 <2442e58> perf: tform: use NCOPY for an expensive copy in PutToMaster d93c202 <d93c202> perf: improve copies in InFunction 25d1630 <25d1630> perf: improve copies in PrepPoly 8941fac <8941fac> perf: improve copies in PutBracket, DoIfStatement, Generator, PrepPoly File Changes (6 files <https://github.com/form-dev/form/pull/799/files>) M sources/declare.h <https://github.com/form-dev/form/pull/799/files#diff-6f8d49bdc8f58224062fa24277a820c1bea7ab29bb935d4f755d0697912f50b6> (12) M sources/execute.c <https://github.com/form-dev/form/pull/799/files#diff-f625dc8f12d0c293df79fc18df8fb1340aeaabdbc09efe3e9a06d7c88773bf26> (4) M sources/if.c <https://github.com/form-dev/form/pull/799/files#diff-5f3f8762053cab97ba35c5105c4cde000ac3a0f93f3d8028da1649f55cf550f1> (2) M sources/proces.c <https://github.com/form-dev/form/pull/799/files#diff-7d9b915201d0ad01f5242de4aa4a2660d84d7c66ffe4b2a3b44e68628709f931> (62) M sources/sort.c <https://github.com/form-dev/form/pull/799/files#diff-fe8d53f77e0481de37e05715c6377529b32237680a601ddf3ea1b4530b15d604> (6) M sources/threads.c <https://github.com/form-dev/form/pull/799/files#diff-bc875f2135c9865c088b27fae715e0b913cef31c269e97c0b79fcf84b4c77f8c> (6) Patch Links: https://github.com/form-dev/form/pull/799.patch https://github.com/form-dev/form/pull/799.diff — Reply to this email directly, view it on GitHub <#799>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABJPCETWJLAARBOMXN2SNIT4L4OJXAVCNFSM6AAAAACVEDYHOKVHI2DSMVQWIX3LMV43ASLTON2WKOZTHE2DCNBUGMZTCNA>. You are receiving this because you are subscribed to this thread.

[coveralls]

coverage: 58.029% (-0.01%) from 58.043%
when pulling c5931f9 on jodavies:memmove
into c134010 on form-dev:master.

[jodavies]

I ran benchmarks with more samples, I think indeed the use of memmove doesn't lead to a measurable performance difference. I cleaned up the commits to include only the obvious wins and use the original macros.

This results in 6-7% improvement for Forcer, 3% for mincer-exact, 0-1% for everything else.

[tueda]

Coveralls is completely down... See: https://status.coveralls.io/