The Packet16f, Packet8f and Packet8d types are too large to use with dynamically
sized matrices typically processed by the SliceVectorizedTraversal specialization of
the dense_assignment_loop. Using these types is likely to lead to little or no
vectorization. Significant slowdown in the multiplication of these small matrices can
be observed when building with AVX and AVX512 enabled.
This patch introduces a new dense_assignment_kernel that is used when
computing small products whose operands have dynamic dimensions. It ensures that the
PacketSize used is no larger than 4, thereby increasing the chance that vectorized
instructions will be used when computing the product.
I tested all 969 possible combinations of M, K, and N that are handled by the
dense_assignment_loop on x86 builds. Although a few combinations are slowed down
by this patch they are far outnumbered by the cases that are sped up, as the
following results demonstrate.
Disabling Packed8d on AVX512 builds:
Total Cases: 969
Better: 511
Worse: 85
Same: 373
Max Improvement: 169.00% (4 8 6)
Max Degradation: 36.50% (8 5 3)
Median Improvement: 35.46%
Median Degradation: 17.41%
Total FLOPs Improvement: 19.42%
Disabling Packet16f and Packed8f on AVX512 builds:
Total Cases: 969
Better: 658
Worse: 5
Same: 306
Max Improvement: 214.05% (8 6 5)
Max Degradation: 22.26% (16 2 1)
Median Improvement: 60.05%
Median Degradation: 13.32%
Total FLOPs Improvement: 59.58%
Disabling Packed8f on AVX builds:
Total Cases: 969
Better: 663
Worse: 96
Same: 210
Max Improvement: 155.29% (4 10 5)
Max Degradation: 35.12% (8 3 2)
Median Improvement: 34.28%
Median Degradation: 15.05%
Total FLOPs Improvement: 26.02%
- unsupported/Eigen/CXX11/src/Tensor/TensorReductionGpu.h
Changing "pass-by-reference" argument to be "pass-by-value" instead
(in a __global__ function decl).
"pass-by-reference" arguments to __global__ functions are unwise,
and will be explicitly flagged as errors by the newer versions of HIP.
- Eigen/src/Core/util/Memory.h
- unsupported/Eigen/CXX11/src/Tensor/TensorContraction.h
Changes introduced in recent commits breaks the HIP compile.
Adding EIGEN_DEVICE_FUNC attribute to some functions and
calling ::malloc/free instead of the corresponding std:: versions
to get the HIP compile working again
- unsupported/Eigen/CXX11/src/Tensor/TensorReduction.h
Change introduced a recent commit breaks the HIP compile
(link stage errors out due to failure to inline a function).
Disabling the recently introduced code (only for HIP compile), to get
the eigen nightly testing going again.
Will submit another PR once we have te proper fix.
- Eigen/src/Core/util/ConfigureVectorization.h
Enabling GPU VECTOR support when HIP compiler is in use
(for both the host and device compile phases)
