Avx

Advanced Vector Extensions (AVX) is an extension to the x86 instruction set architecture for microprocessors from Intel and AMD.

Sse

SSE (Streaming SIMD Extensions) was the first of many similarly-named vector extensions to the x86 instruction set



Haswell l1d cache

Example

"For small buffers hot in l1d cache avx can copy significantly faster than sse on cpus like haswell where 256b loads stores really do use a 256b data path to l1d cache instead of splitting into two 128b operations"

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SSE-copy, AVX-copy and std::copy performance

"So congratulations - you can pat yourself on the back your avx routine is indeed about a third faster than the sse routine tested on haswell i7 here"

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AVX 256-bit code performing slightly worse than equivalent 128-bit SSSE3 code

Slower version performance

Example

"Rep string instructions and especially the non-rep versions re good for code-size but often slower than sse avx loops"

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Assembly string instructions register DS and ES in real mode

"So the avx version does indeed appear to faster than the sse version both for the original implementations and the optimised implementations"

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Float point multiplication: LOSING speed with AVX against SSE?

"As expected the performance got better with both and avx 2 faster than sse 4.2 but when i profiled the code with papi i found out that the total number of misses mainly l1 and l2 increased a lot"

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Increased number of cache misses when vectorizing code

"The question is avx scalar is 2.7x faster than sse when i vectorized it the speed up is 3x matrix size is 128x128 for this question"

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What is the benefits of using vaddss instead of addss in scalar matrix addition?

"I have code that does the same thing but the avx version is considerably slower than the sse version"

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Float point multiplication: LOSING speed with AVX against SSE?

"Now for sse is clearly faster and for the smaller values it s nearlly as fast as avx"

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Performance of SSE and AVX when both Memory-band width limited

Faster

Example

"So i expect that avx could be faster than sse"

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AVX mat4 inv implementation is slower than SSE

"I expected avx to be about 1.5x faster than sse"

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AVX vs. SSE: expect to see a larger speedup

Others

Example

Ironically ancient x86 instruction rep stosq performs much better than sse and avx in terms of memory copy

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SSE-copy, AVX-copy and std::copy performance

The underlying reason for this and various other avx limitations is that architecturally avx is little more than two sse execution units side by side - you will notice that virtually no avx instructions operate horizontally across the boundary between the two 128 bit halves of a vector which is particularly annoying in the case of vpalignr

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Intel AVX : Why is there no 256-bits version of dot product for double precision floating point variables?

And simd math libraries for sse and avx however they seem to be more sse than avx2

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Efficient implementation of log2(__m256d) in AVX2

Also note that the fact that the avx are a newer than sse doesn t make the avx faster whatever you are planning to use the number of cycles taken by an function is probably more important than the avx vs sse argument for example see this answer

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SSE-copy, AVX-copy and std::copy performance

Either it s a problem with mixing sse avx without vzeroupper maybe you compiled the rest of your code with or something and double-precision math is using avx;or your sse version is bigger and causes i-cache misses

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Balancing SSE & FPU

We have to mask anyway for widths lower than 16-bit sse avx doesn t have byte-granularity shifts only 16-bit minimum. benchmark results on arch linux i7-6700k from njuffa s test harness with this added

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Count each bit-position separately over many 64-bit bitmasks, with AVX but not AVX2

I know this does not answer your core question why avx is slower but since your ultimate goal is fast popcount the avx - sse comparison is irrelevant as both are inferior to the builtin popcount

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AVX 256-bit code performing slightly worse than equivalent 128-bit SSSE3 code

Buf1 buf2 and buf3 is small enough to located in l1 cache and l2 cache l2 cache 1mb .both of sse and avx is band width limited but with the datalen increase why do the avx need more time than sse

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Performance of SSE and AVX when both Memory-band width limited

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