Even though the example is contrived, and hopefully not too many people are doing massive reductions using a linked list of random pointers, it would still be n

Even though the example is contrived, and hopefully not too many people are doing massive reductions using a linked list of random pointers, it would still be nice to offer some suggestion on what alternatives there are. Maybe it’s faster to collect all the pointers into an array and use the first loop? If ‘list’ entries are consecutive in memory, you can ignore the list order and consume them in memory order. Collecting and sorting the pointers might improve the cache hit rates, especially if the values are dense in memory. For anything performance sensitive, avoiding linked lists, especially non-intrusive linked lists, is often a good idea, right? What’s with the “if (idx == NULLPTR)” block? The loop won’t access an entry outside the list, so this appears to be adding unnecessary instructions and unnecessary divergence. (And maybe even unnecessary dependencies?) Does demonstrating the performance problem depend on having this code in the loop? I hope not, but I’m very curious why it’s there. A couple of other tiny nits - the first 2 graphs should have a Y axis that starts at zero! That won’t compromise these in any way. There should be a very compelling reason not to show ratios on a graph that start from zero, and these don’t have any such reason. And I’m curious why the X axis is factors of 8 except the last two, which seem strangely arbitrary?