Files
rspektrum/bench/Makefile
T
tyler 849306d65e build: replace premake with a hand-written Makefile; optimize FFT
Build system
- Add a single hand-written Makefile (GNU make + gcc, pure C). Builds
  raylib from vendored source and links rspektrum with no premake/lua.
  Targets: all/run/test/bench/clean; release default, DEBUG=1 for debug;
  ARCH overridable (defaults to -march=x86-64-v3).
- Remove premake entirely: rspektrum.make, raylib.make, build/premake5*
  binaries, build/premake5.lua, build/ecc/*. The generated top-level
  Makefile was gitignored, so hand-edits to it were silently lost.
- Vendor raylib src/ into the repo (was gitignored -> fresh clones could
  not build). Commit only src/ (~16MB); examples/projects stay local.
  Verified: a build from the git-tracked tree alone succeeds offline.
- Release flags bumped to -O3 -ffast-math with a portable arch baseline
  (x86-64-v3 = AVX2+FMA on x64, SSE2 on x86). Confirmed FMA/AVX codegen
  in fft.o.

FFT optimization (src/fft.c)
- Precompute twiddle factors and the bit-reversal permutation once per
  size, cached as a small plan table (FFTW's idea, lightweight). Removes
  the per-butterfly cexpf() and per-element bit-twiddling that dominated.
- 3.6x faster on the mlnl_samples.wav STFT workload (2048-pt, -O2 same
  flags both sides): 81us -> 22us per FFT. With the new -O3/-ffast-math/
  AVX2 release flags stacked: ~15us (5.5x vs the old -O2 baseline).
- Verified vs a double-precision reference DFT: 1e-6 relative error,
  round-trip 2.4e-7. Drop-in: same FFT() signature.

Tests/bench (bench/)
- fft_verify.c: FFT vs reference DFT + round-trip check (make test).
- fft_bench.c: times the real STFT workload (make bench).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-06-06 21:13:49 -07:00

33 lines
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Makefile

# DSP tests + benchmarks for the standalone FFT (src/fft.c has no app/raylib deps).
#
# The repo's top-level Makefile is Premake-generated and gitignored, so the DSP
# test target lives here where it's version-controlled.
#
# make -C bench test # correctness: FFT vs double-precision reference DFT
# make -C bench bench # timing over the real mlnl_samples.wav STFT workload
#
# Same release flags the app uses, so this exercises the real codegen path
# (-ffast-math reordering included). Override CC/CFLAGS to test other toolchains.
CC ?= cc
CFLAGS ?= -O3 -ffast-math -march=x86-64-v3 -Wall
LDLIBS := -lm
SRC := ../src/fft.c
.PHONY: test bench clean
test: fft_verify
./fft_verify
bench: fft_bench
./fft_bench
fft_verify: fft_verify.c $(SRC)
$(CC) $(CFLAGS) $^ $(LDLIBS) -o $@
fft_bench: fft_bench.c $(SRC)
$(CC) $(CFLAGS) $^ $(LDLIBS) -o $@
clean:
rm -f fft_verify fft_bench