Fast homogeneous and rotation matrix multiplications #1845
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Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## master #1845 +/- ##
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- Coverage 47.84% 33.35% -14.50%
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Files 532 466 -66
Lines 68944 66167 -2777
Branches 32201 28740 -3461
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- Hits 32986 22068 -10918
- Misses 31908 33587 +1679
- Partials 4050 10512 +6462 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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modules/core/src/math/transformation/vpHomogeneousMatrix.cpp:60:13: warning: unused variable 'outputData' [-Wunused-variable]
60 | double *outputData = output.data;
| ^~~~~~~~~~
modules/tracker/rbt/src/features/vpRBDenseDepthTracker.cpp:200:10: warning: variable 't1' set but not used [-Wunused-but-set-variable]
200 | double t1 = vpTime::measureTimeMs();
| ^
…able Document vpRotationMatrix::rotateVectors() method
…able Document vpHomogeneousMatrix::project() method
modules\core\src\math\transformation\vpRotationMatrix.cpp(128,21): error: always_inline function '_mm_hadd_pd' requires target feature 'sse3', but would be inlined into function 'rotateVectors' that is compiled without support for 'sse3'
128 | __m128d r01 = _mm_hadd_pd(mul0, mul1);
| ^
s-trinh
reviewed
Dec 7, 2025
Comment on lines
+97
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| #if defined(VISP_HAVE_AVX2) | ||
| using Register = __m512d; | ||
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| inline constexpr int numLanes = 8; | ||
| inline const Register add(const Register a, const Register b) | ||
| { | ||
| return _mm512_add_pd(a, b); | ||
| } |
Contributor
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Two comments.
AVX2 != 512-bits register:
- AVX / AVX2 improvements: https://fr.wikipedia.org/wiki/Advanced_Vector_Extensions#Advanced_Vector_Extensions_2
- see AVX-512 and all the different flavors
- you can use
cat /proc/cpuinfoto see which AVX-512 variants your CPU has
I would definitely not expose SIMD code to the user:
- people knowing this subject will not use this code and there are already better libs doing that
- with SIMD code in
.h, withmarch=nativeand running ViSP on another computer there are some chances to have SIGILL crash on old CPU - I think what is done is runtime dispatching:
- the
.socan have all the more advanced instructions set - for example for a convolution function, a variant for 128-bits, 256-bits and 512-bits (the lib size will increase a lot)
- and at runtime you check if the CPU has this kind of instructions set and dispatch to the more advanced one
- the
For the moment this file is duplicated in core and rbt modules. We should find a solution to avoid code duplication.
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This PR introduces two methods that perform batched 3d point transformations:
vpHomogeneousMatrix::project: Project N 3d points (Represented as a Nx3 vpMatrix) from a frame to anothervpRotationMatrix::rotateVectors: Rotate Vectors (Represented as a Nx3)These methods rely on explicit mat muls and SIMD operations to be faster. This PR adds tests to measure the speed up against two naive versions: the Naive
vpColVector pa = T * pbloop andvpMatrix::mult2Matricesversion (which multiplies a 4x4 matrix with an 4xN matrix.Interestingly, the version without SIMD in
projectorrotateVectors, already provides a x2/x3 speedup, while on my machine, I can obtain x5,x6 speedups.Some notes:
march=nativeflag. As it is, turning on AVX with-mavxdoes not turn on FMA. This also enables all SSE relevant feature sets, which could help simplify the compileflags.