avx2

问题 I've got an application that requires AVX2 to work correctly. A check was implemented to check during application start if CPU has AVX2 instruction. I would like to check if it works correctly, but i only have CPU that has AVX2. Is there a way to temporarly turn it off for testing purposes? Or to somehow emulate other CPU? 回答1: Yes, use an "emulation" (or dynamic recompilation) layer like Intel's Software Development Emulator (SDE), or maybe QEMU. SDE is closed-source freeware, and very handy

问题 I have two __m256i vectors, filled with 32 8-bit integers. Something like this: __int8 *a0 = new __int8[32] {2}; __int8 *a1 = new __int8[32] {3}; __m256i v0 = _mm256_loadu_si256((__m256i*)a0); __m256i v1 = _mm256_loadu_si256((__m256i*)a1); How can i multiply these vectors, using something like _mm256_mul_epi8(v0, v1) (which does not exist) or any another way? I want 2 vectors of results, because the output element width is twice the input element width. Or something that works similarly to

问题 I have two __m256i vectors, filled with 32 8-bit integers. Something like this: __int8 *a0 = new __int8[32] {2}; __int8 *a1 = new __int8[32] {3}; __m256i v0 = _mm256_loadu_si256((__m256i*)a0); __m256i v1 = _mm256_loadu_si256((__m256i*)a1); How can i multiply these vectors, using something like _mm256_mul_epi8(v0, v1) (which does not exist) or any another way? I want 2 vectors of results, because the output element width is twice the input element width. Or something that works similarly to

问题 I'm trying to pack 16 bits data to 8 bits by using _mm256_shuffle_epi8 but the result i have is not what i'm expecting. auto srcData = _mm256_setr_epi8(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32); __m256i vperm = _mm256_setr_epi8( 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1); auto result = _mm256_shuffle_epi8(srcData, vperm); I'm expecting

问题 I'm trying to pack 16 bits data to 8 bits by using _mm256_shuffle_epi8 but the result i have is not what i'm expecting. auto srcData = _mm256_setr_epi8(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32); __m256i vperm = _mm256_setr_epi8( 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1); auto result = _mm256_shuffle_epi8(srcData, vperm); I'm expecting

问题 I want to store the 8 integers from a __m256i variable to an array of 8 x 32 bit int s. I thought the instruction for that would be _mm256_store_epi32 , but I get an error that this instruction doesn't even exist! 回答1: Have a look at the Intel Intrinsics Guide. Depending on whether your destination is aligned, you need _mm256_store_si256 or _mm256_storeu_si256. 来源： https://stackoverflow.com/questions/43304021/what-is-the-avx2-instruction-to-store-8-integers

问题 How to deal with SIGSEGV, Segmentation fault. while using Avx2 (_mm256_load_pd)(_mm256_store_pd) (solved) _mm256_load_pd I've received segmentation fault wile called _mm256_load_pd usage are as blew double * Val = malloc(sizeof(double)*4); __m256d vecv = _mm256_load_pd(&Val[0]); gdb shows Program received signal SIGSEGV, Segmentation fault. 0x00007ffff7fc5017 in _mm256_load_pd (__P=0x555555559370) at /usr/lib/gcc/x86_64-linux-gnu/9/include/avxintrin.h:862 862 return *(__m256d *)__P; (gdb)

问题 We have a translation unit we want to compile with AVX2 (only that one): It's telling GCC upfront, first line in the file: #pragma GCC target "arch=core-avx2,tune=core-avx2" This used to work with GCC 4.8 and 4.9 but from 6 onward (tried 7 and 8 too) we get this warning (that we treat as an error): error: SSE instruction set disabled, using 387 arithmetics On the first function returning a float. I have tried to enable back SSE 4.2 (and avx and avx2) like so #pragma GCC target "sse4.2,arch

问题 I have two __m256i vectors (each containing chars), and I want to find out if they are completely identical or not. All I need is true if all bits are equal, and 0 otherwise. What's the most efficient way of doing that? Here's the code loading the arrays: char * a1 = "abcdefhgabcdefhgabcdefhgabcdefhg"; __m256i r1 = _mm256_load_si256((__m256i *) a1); char * a2 = "abcdefhgabcdefhgabcdefhgabcdefhg"; __m256i r2 = _mm256_load_si256((__m256i *) a2); 回答1: The most efficient way on current Intel and

问题 I have two __m256i vectors (each containing chars), and I want to find out if they are completely identical or not. All I need is true if all bits are equal, and 0 otherwise. What's the most efficient way of doing that? Here's the code loading the arrays: char * a1 = "abcdefhgabcdefhgabcdefhgabcdefhg"; __m256i r1 = _mm256_load_si256((__m256i *) a1); char * a2 = "abcdefhgabcdefhgabcdefhgabcdefhg"; __m256i r2 = _mm256_load_si256((__m256i *) a2); 回答1: The most efficient way on current Intel and