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perf: back the CPU similarity GEMM with OpenBLAS

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The CPU path was a scalar triple loop. It is the correctness oracle for the GPU
backends, but it is also what CI runs — there is no GPU on the N100 host — and
since AR-003 removed the per-frame face cap, a crowded frame now scores many
faces against a library-scale gallery. Scoring one face against 5000 embeddings
is 2.6 MFLOP; in scalar that does not hold up (AR-027).

S(g,f) viewed as row-major [n_faces x n_gallery] is exactly query * gallery^T,
so the loop nest collapses into a single cblas_sgemm.

OpenBLAS is optional in the build: found via pkg-config, and the scalar path
remains when it is absent so no hard dependency is added and the two can be
diffed when a similarity looks wrong. The configure step warns rather than
failing, since a developer without it should still get a working tree.

The test target links it too. Without that the suite compiles the scalar
fallback while the builder image ships CBLAS, so CI would be verifying a kernel
that is not the one running in production — the same class of mistake as testing
a path the gate never executes.

Recorded as required (not optional) in the DP-007 image, for the same reason.

Suite: 92 cases, 6136 assertions, with CBLAS compiled in.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

TRACES: AR-026, AR-027, DP-007 | SR-001
This commit is contained in:
dtourolle
2026-07-31 15:04:29 +02:00
co-authored by Claude Opus 5
parent 13bdc27566
commit cc1bed92d8
8 changed files with 325 additions and 17 deletions
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tests/CMakeLists.txt
+13
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@@ -34,7 +34,20 @@ target_include_directories(sae_tests PRIVATE ${CMAKE_SOURCE_DIR}/src)
# SAE_MODELS_DIR: config.hpp (pulled in by track_gallery.hpp) bakes model paths.
# SAE_TEST_FIXTURES_DIR: the audio golden vector is read from the source tree,
# not copied, so the file the plugin repo shares is the file under test.
# AR-026/AR-027: exercise the same kernel CI actually runs. Without this the
# suite compiles the scalar fallback while the CPU builder image links OpenBLAS,
# so the tested path and the shipped path would differ.
find_package(PkgConfig QUIET)
if(PkgConfig_FOUND)
pkg_check_modules(OPENBLAS_T QUIET openblas)
endif()
if(OPENBLAS_T_FOUND)
target_include_directories(sae_tests PRIVATE ${OPENBLAS_T_INCLUDE_DIRS})
target_link_libraries(sae_tests PRIVATE ${OPENBLAS_T_LINK_LIBRARIES})
endif()
target_compile_definitions(sae_tests PRIVATE
$<$<BOOL:${OPENBLAS_T_FOUND}>:SAE_GEMM_CBLAS>
SAE_GEMM_CPU
SAE_MODELS_DIR="${SAE_MODELS_DIR}"
SAE_TEST_FIXTURES_DIR="${CMAKE_CURRENT_SOURCE_DIR}/fixtures")