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I am not sure what you call "auto-vectorization". The auto-vectorization that I know of is the ability of a compiler to batch several scalar operations of a se

I am not sure what you call "auto-vectorization". The auto-vectorization that I know of is the ability of a compiler to batch several scalar operations of a sequential loop into one single vector operation (SSE). There is still only one processor/core at work, but it processes several items at once. OpenMP is a standard to ease multithreading, to use several parallel threads (cores) without the trouble of creating threads by hand. Edit: SIMD auto-vectorization directives are part of OpenMP 4, released 2 years ago. https://software.intel.com/en-us/blogs/2012/11/05/openmp-40-may-offer-important-solutions-for-targeting-and-vectorization https://software.intel.com/en-us/blogs/2012/11/05/openmp-40-...

DannyBee 11y ago
So, auto-vectorization and auto-parallelization are closely related problems in compilers. The legality necessary to do either is mostly the same (the profitability is very different) ICC used to do both. Now they mainly focus on vectorization. The main reason that auto-vectorization is much more "advanced" is many-fold: 1. Most cores have more resources for auto-vectorization than parallelization. 2. Auto-parallelization has more communication overhead, and as you scale, communication overhead dominates, so doing both at once doesn't help as much as you'd think.