4 ms·

Last time i looked at intel scatter/gather I got the impression it only works for a very narrow use case, and getting it to perform wasn’t easy. Did I miss some

• narrowbyte 2y ago
  The post says, about SIMT / GPU programming, "This loss results from the DRAM architecture quite directly, the GPU being unable to do much about it – similarly to any other processor." I would say that for SIMD the situation is basically the same. gather/scatter don't magically make the memory hierarchy a non-issue, but they're no longer adding any unnecessary pain on top.
  • yosefk 2y ago
    Barrel threaded machines like GPUs have easier time hiding the latency of bank conflict resolution when gathering/scattering against local memory/cache than a machine running a single instruction thread. So pretty sure they have a fundamental advantage when it comes to the throughput of scatter/gather operations that gets bigger with a larger number of vector lanes
• majke 2y ago
  vpgatherdd - I think that for newer CPUs it is faster than many loads + inserts, but if you are going to fault a lot, then it becomes slow. > The VGATHER instructions are implemented as micro-coded flow. Latency is ~50 cycles. https://www.intel.com/content/www/us/en/content-details/814198/intel-64-and-ia-32-architectures-optimization-reference-manual-volume-1.html https://www.intel.com/content/www/us/en/content-details/8141...