On Tue, Jul 9, 2024, at 14:01, Dean Rasheed wrote: > One thing I noticed while testing the earlier patches on this thread > was that they were significantly faster if they used unsigned integers > rather than signed integers. I think the reason is that operations > like "x / 10000" and "x % 10000" use fewer CPU instructions (on every > platform, according to godbolt.org) if x is unsigned. > > In addition, this reduces the number of times the digit array needs to > be renormalised, which seems to be the biggest factor. > > Another small optimisation that seems to be just about worthwhile is > to pull the first digit of var1 out of the main loop, so that its > contributions can be set directly in dig[], rather than being added to > it. This allows palloc() to be used to allocate dig[], rather than > palloc0(), and only requires the upper part of dig[] to be initialised > to zeros, rather than all of it. > > Together, these seem to give a decent speed-up: .. > Attachments: > * optimise-mul_var.patch
I've reviewed the patch now. Code is straightforward, and comments easy to understand. LGTM. Regards, Joel
