Vectorization, dependencies and outer loop vectorization: if you can’t beat them, join them

Vectorization, dependencies and outer loop vectorization: if you can’t beat them, join them

As I already mentioned in earlier posts, vectorization is the holy grail of software optimizations: if your hot loop is efficiently vectorized, it is pretty much running at fastest possible speed. So, it is definitely a goal worth pursuing, under two assumptions: (1) that your code has a hardware-friendly memory access pattern1 and (2) that…

When vectorization hits the memory wall: investigating the AVX2 memory gather instruction

When vectorization hits the memory wall: investigating the AVX2 memory gather instruction

For all the engineers who like to tinker with software performance, vectorization is the holy grail: if it vectorizes, this means that it runs faster. Unfortunately, many times this is not the case, and the results of forcing vectorization by any means can mean lower performance. This happens when vectorization hits the memory wall: although…

The price of dynamic memory: Memory Access

The price of dynamic memory: Memory Access

If your program uses dynamic memory, its speed will depend on allocation time but also on memory access time. Here we investigate how memory access time depends on the memory layout of your data structure. We also investigate ways to speed up your program by laying out your data structure optimally.