Intel® Advanced Vector Extensions

Extract non-zero byte from _m128i


I have 4 _m128i 64byte elements which can contain 0 or non-zero (+ve, -ve) values. I want to extract non-zero values from them.

I looked at _mm_extract_epi8/_mmextract_epi16 but the syntax is int _mm_extract_epi16 (__m128i a, int imm) where imm is the index, hence I have to loop to get non-zero values.

Any intrinsics functions that can be used to avoid loop will be helpful. Inputs appreciated.


Is it ok to create an array of _m256i

Hi all! I am parallelizing a certain dynamic programming problem using AVX2.
In the main iteration of my calculation, I calculate column in matrix where each cell is an AVX2 register -> _m256i. I use values from the previous matrix column as input values for calculating the current column. Columns can be big, so what I do is I have an array of _m256i values, like this: _m256i prevColumn [N].

Cache and _mm_prefetch


I have some code, where I iterate over an array in reverse order. I already use SSE,AVX (depending on what CPU supports). Normally prefetching of CPU should be finde, if I iterate over an arry from begin to end. But what about end to begin, so reverse? Does the CPU realize this pattern?

Or should I give hints, with _mm_prefetch? If so, how do I use this intrinsic. Should I always give L1 as cache level. And how many iterations before should I prefetch data?

Improve Server Application Performance with Intel® Advanced Vector Extensions 2

The Intel® Xeon® processor E7 v3 family now includes an instruction set called Intel® Advanced Vector Extensions 2 (Intel® AVX2), which can potentially improve application performance related to high performance computing, databases, and video processing. To validate this statement, I performed a simple experiment using the Intel® Optimized LINPACK benchmark. The results, as shown in Table 1, show a greater than 2x performance increase using Intel AVX2 vs.

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