avx

问题 I have _m256i vectors that contain 10-bit words inside 16-bit integers (so 16*16-bit containing only 16*10 useful bits). What is the best/fastest way to extract only those 10-bits and pack them to produce an output bitstream of 10-bit values? 回答1: Here’s my attempt. Have not benchmarked, but I think it should work pretty fast overall: not too many instructions, all of them have 1 cycle of latency on modern processors. Also the stores are efficient, 2 store instructions for 20 bytes of data.

问题 I have _m256i vectors that contain 10-bit words inside 16-bit integers (so 16*16-bit containing only 16*10 useful bits). What is the best/fastest way to extract only those 10-bits and pack them to produce an output bitstream of 10-bit values? 回答1: Here’s my attempt. Have not benchmarked, but I think it should work pretty fast overall: not too many instructions, all of them have 1 cycle of latency on modern processors. Also the stores are efficient, 2 store instructions for 20 bytes of data.

问题 I have _m256i vectors that contain 10-bit words inside 16-bit integers (so 16*16-bit containing only 16*10 useful bits). What is the best/fastest way to extract only those 10-bits and pack them to produce an output bitstream of 10-bit values? 回答1: Here’s my attempt. Have not benchmarked, but I think it should work pretty fast overall: not too many instructions, all of them have 1 cycle of latency on modern processors. Also the stores are efficient, 2 store instructions for 20 bytes of data.

问题 I am trying to do left rotation of a 128 bit number in AVX2. Since there is no direct method of doing this, I have tried using left shift and right shift to accomplish my task. Here is a snippet of my code to do the same. l = 4; r = 4; targetrotate = _mm_set_epi64x (l, r); targetleftrotate = _mm_sllv_epi64 (target, targetrotate); The above c ode snippet rotates target by 4 to the left. When I tested the above code with a sample input, I could see the result is not rotated correctly. Here is

问题 I am trying to do left rotation of a 128 bit number in AVX2. Since there is no direct method of doing this, I have tried using left shift and right shift to accomplish my task. Here is a snippet of my code to do the same. l = 4; r = 4; targetrotate = _mm_set_epi64x (l, r); targetleftrotate = _mm_sllv_epi64 (target, targetrotate); The above c ode snippet rotates target by 4 to the left. When I tested the above code with a sample input, I could see the result is not rotated correctly. Here is

问题 I'm currently trying to compile software for the use on a HPC-Cluster using Intel compilers. The login-node, which is where I compile and prepare the computations uses Intel Xeon Gold 6148 Processors, while the compute nodes use either Haswell- (Intel Xeon E5-2660 v3 / Intel Xeon Processor E5-2680 v3) or Skylake-processors (Intel Xeon Gold 6138). As far as I understand from the links above, my login-node supports Intel SSE4.2, Intel AVX, Intel AVX2, as well as Intel AVX-512 but my compute

问题 I'm currently trying to compile software for the use on a HPC-Cluster using Intel compilers. The login-node, which is where I compile and prepare the computations uses Intel Xeon Gold 6148 Processors, while the compute nodes use either Haswell- (Intel Xeon E5-2660 v3 / Intel Xeon Processor E5-2680 v3) or Skylake-processors (Intel Xeon Gold 6138). As far as I understand from the links above, my login-node supports Intel SSE4.2, Intel AVX, Intel AVX2, as well as Intel AVX-512 but my compute

问题 I'm currently trying to compile software for the use on a HPC-Cluster using Intel compilers. The login-node, which is where I compile and prepare the computations uses Intel Xeon Gold 6148 Processors, while the compute nodes use either Haswell- (Intel Xeon E5-2660 v3 / Intel Xeon Processor E5-2680 v3) or Skylake-processors (Intel Xeon Gold 6138). As far as I understand from the links above, my login-node supports Intel SSE4.2, Intel AVX, Intel AVX2, as well as Intel AVX-512 but my compute

问题 I'm currently trying to compile software for the use on a HPC-Cluster using Intel compilers. The login-node, which is where I compile and prepare the computations uses Intel Xeon Gold 6148 Processors, while the compute nodes use either Haswell- (Intel Xeon E5-2660 v3 / Intel Xeon Processor E5-2680 v3) or Skylake-processors (Intel Xeon Gold 6138). As far as I understand from the links above, my login-node supports Intel SSE4.2, Intel AVX, Intel AVX2, as well as Intel AVX-512 but my compute

问题 I'm trying to understand the VEX prefix encoding for the SSE/AVX instructions. So please bear with me if I ask something simple. I have the following related questions. Let's take the MOVUP(D/S) instruction ( 0F 10 ). If I follow the 2-byte VEX prefix encoding correctly: The following two instruction encodings produce the same result: db 0fh, 10h, 00000000b ; movups xmm0,xmmword ptr [rax] db 0c5h, 11111000b, 10h, 00000000b ; vmovups xmm0,xmmword ptr [rax] As these two: db 066h, 0fh, 10h,