simd

问题 I was inspired by this link https://www.sigarch.org/simd-instructions-considered-harmful/ to look into how AVX512 performs. My idea was that the clean up loop after the loop could be removed using the AVX512 mask operations. Here is the code I am using void daxpy2(int n, double a, const double x[], double y[]) { __m512d av = _mm512_set1_pd(a); int r = n&7, n2 = n - r; for(int i=-n2; i<0; i+=8) { __m512d yv = _mm512_loadu_pd(&y[i+n2]); __m512d xv = _mm512_loadu_pd(&x[i+n2]); yv = _mm512_fmadd

问题 In my code I solve integral y=x^2-4x+6 I used SSE - it allows me to operate on 4 values in one time. I made program which solve this integral with values from 0 to 5 divided to five 4-element vectors n1, n2, n3, n4. .data n1: .float 0.3125,0.625,0.9375,1.25 n2: .float 1.5625,1.875,2.1875,2.5 n3: .float 2.8125,3.12500,3.4375,3.75 n4: .float 4.0625,4.37500,4.6875,5 szostka: .float 6,6,6,6 czworka: .float 4,4,4,4 .text .global main main: movups (n1),%xmm0 mulps %xmm0,%xmm0 movups (szostka),%xmm2

问题 How do I use the Intel AVX vector instruction set from Java? It's a simple question but the answer seems to be hard to find. 回答1: As I know, most current Java JVM JITters don't support automatic vectorization or just do that for very simple loops, so you're out of luck. In Mono's .NET implementation there's Mono.Simd for manual vector code emission and then later MS introduced the System.Numeric.Vectors . Unfortunately there's nothing similar in Java. I don't know if Java's vector class is

问题 I have tried AVX intrinsics. But it caused "Unhandled exception at 0x00E01555 in test.exe: 0xC000001D: Illegal Instruction." I used Visual studio 2015. And the exception error is caused at "vfmadd213ps ymm2,ymm1,ymm0" instruction. I have tried set "/arch:AVX" and "/arch:AVX2", but still error caused. Below is my code. #include <immintrin.h> int main(int argc, char *argv[]) { float a[8] = { 0 }; float b[8] = { 0 }; float c[8] = { 0 }; __m256 _a = _mm256_loadu_ps(a); __m256 _b = _mm256_loadu_ps

问题 According to https://sourceware.org/glibc/wiki/libmvec GCC has vector implementation of math functions. They can be used by compiler for optimizations, it can be seen in this example: https://godbolt.org/g/IcxtVi, compiler uses some mangled sine function and operates on 4 doubles at a time I know that there are SIMD math libraries that can be used if I need math functions, but I am still interested is there a way to manually call vectorized math functions that already exist in GCC on __m256d

问题 In a piece of C++ code that does something similar to (but not exactly) matrix multiplication, I load 4 contiguous doubles into 4 YMM registers like this: # a is a 64-byte aligned array of double __m256d b0 = _mm256_broadcast_sd(&b[4*k+0]); __m256d b1 = _mm256_broadcast_sd(&b[4*k+1]); __m256d b2 = _mm256_broadcast_sd(&b[4*k+2]); __m256d b3 = _mm256_broadcast_sd(&b[4*k+3]); I compiled the code with gcc-4.8.2 on a Sandy Bridge machine. Hardware event counters (Intel PMU) suggests that the CPU

问题 I have a problem with converting the image data stored in byte[] array to grayscale. I want to use vector SIMD operations because in future a need to write ASM and C++ DLL files to measure operations time. When I read about SIMD I found that SSE command is operation on 128-bit registers so there is a problem because I need to convert my byte[] array into few Vector<T> stored into List<T>. Image is four channels RGBA JPEG so I need also to know how to create vectors with R, G, B data based on

问题 I have a problem with converting the image data stored in byte[] array to grayscale. I want to use vector SIMD operations because in future a need to write ASM and C++ DLL files to measure operations time. When I read about SIMD I found that SSE command is operation on 128-bit registers so there is a problem because I need to convert my byte[] array into few Vector<T> stored into List<T>. Image is four channels RGBA JPEG so I need also to know how to create vectors with R, G, B data based on

问题 I have a problem with converting the image data stored in byte[] array to grayscale. I want to use vector SIMD operations because in future a need to write ASM and C++ DLL files to measure operations time. When I read about SIMD I found that SSE command is operation on 128-bit registers so there is a problem because I need to convert my byte[] array into few Vector<T> stored into List<T>. Image is four channels RGBA JPEG so I need also to know how to create vectors with R, G, B data based on

问题 In SSE3, the PALIGNR instruction performs the following: PALIGNR concatenates the destination operand (the first operand) and the source operand (the second operand) into an intermediate composite, shifts the composite at byte granularity to the right by a constant immediate, and extracts the right-aligned result into the destination. I'm currently in the midst of porting my SSE4 code to use AVX2 instructions and working on 256bit registers instead of 128bit. Naively, I believed that the