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testdata: compare NaN results with the same machine's scalar build - #8
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abs_sqrt.txt, activation_temp.txt and invariant_call.txt compare both builds with testmain/output, which was recorded on amd64. A NaN that an operation creates (the square root of a negative number, 0 times infinity) has the sign bit set on amd64 and clear on arm64, so on arm64 the scalar program itself does not match the recording and the scripts fail before the simd build runs. The recording is now compared only on amd64. On every target the simd build is compared with the scalar build of the same machine, which is the property these scripts check: the rewrite produces the same bits the scalar loop does there.
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Thanks! I was under the impression arm64 tests were running on CI via QEMU emulation. I have to confirm if qemu emulation is broken or simply doesn't run for the baseline tests. |
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The only arm64 coverage in CI was tsvc-test-qemu-arm64, which runs TestGolden in ./tsvc. The testdata scripts never ran on arm64, so abs_sqrt.txt, activation_temp.txt and invariant_call.txt compared arm64 output against an amd64 recording, and nothing caught it until the suite was run on an M4 (fixed in #8). This change adds test-qemu-arm64, which runs go test ./... for GOARCH=arm64 under qemu-aarch64-static, the same way the tsvc target does. It is make test without -race, which needs cgo. Unlike TestGolden, the scripts and tsvc's TestCoverage run the arm64 binaries they build, so the target also needs an aarch64 binfmt handler; on Ubuntu, installing qemu-user-static registers one. The target is added to ci and to the workflow, after qemu is installed.
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`flag_diff.txt` fails on macOS. The `-d` headers carry `diff`'s timestamp, and BSD diff prints it differently from GNU diff (no fractional seconds, no zone). It's the timestamp of a temp file anyway, so it doesn't tell the reader anything. This passes `-L path` for both sides (GNU, BSD and busybox diff all have it), so the headers are just `--- path` / `+++ path` like `gofmt -d`, and the filename replacement goes away. The four diff scripts now expect the path alone. It's one of three small fixes to get the suite passing on macOS, along with #8 and #9, which I needed while trying loopvec on [goav1](https://github.com/thesyncim/goav1). Co-authored-by: Mauri de Souza Meneguzzo <mauri870@gmail.com>
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…alar build (#17) `activation_functions.txt` hashes float bits and compares both builds with `testmain/output`, which was recorded on amd64. It passes on arm64 only because none of its loops creates a NaN: they just pass the input NaN through. With an alpha of 0, `LeakyReLU` computes `0 * -Inf`. The resulting NaN has the sign bit set on amd64 and clear on arm64, so the script fails on arm64 against the recording. This change gives it #8's treatment: the recording is compared only on amd64, and on every target the simd build is compared with the scalar build of the same machine. It also changes the three scripts from #8: - They compared the simd build with the recording on amd64 as well. That adds nothing: on amd64 the scalar build matches the recording and the simd build matches the scalar build. - That comparison came last, so it was the one `-update` recorded. A simd build that differed from the scalar one would have been written into the recording. Now only the scalar build is compared with the recording, and that's what `-update` records. - Two of their comments named the square root of a negative number, though those scripts have no square root. Tested locally: - I made temporary copies of the old and new `activation_functions.txt` with alpha set to 0, recorded the expected output on amd64, and ran both on arm64 under qemu. The old script fails at `cmp stdout testmain/output`, and the new one passes. - The four scripts pass on amd64 and on arm64 under qemu, and `-update` leaves them unchanged.
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abs_sqrt.txt,activation_temp.txtandinvariant_call.txtcompare both builds againsttestmain/output, which was recorded on amd64. A NaN produced by an operation (sqrt of a negative number, 0 × Inf) has the sign bit set on amd64 (0xffc00000) and clear on arm64 (0x7fc00000). So on arm64 even the scalar run differs from the recording, and the scripts fail before they get to the simd build.What these scripts check is that the rewrite gives the same bits as the scalar loop on the machine running it. Now the recording is only compared on amd64, and on every target the simd output is compared against the scalar output saved on the same machine.
-updateonly rewrites sections that already exist, soscalar.outnever becomes a golden.Found while running the suite on an M4 for goav1.