These days sage.math is often operating with all 16 cores going flat out. When it gets like this, FLINT slows down dramatically, but MAGMA does not. This makes timing comparisons meaningless (and slows down development).
I'm wondering if anyone has any suggestions as to why this might be. How can their code take the same user time whether the machine is under load or not, and ours takes up to 50% longer. I've checked the following things: 1) Cache hints: We are already using these as these make a noticeable difference. My theory about this is that when the kernel switches between different processes, any computation that was underway gets moved out of cache and the cache gets overwritten by the other process. Cache hints help by making sure cache coherency is optimised for the currently active process. 2) Nice number: MAGMA runs at a default nice level of -5 as does FLINT. 3) Memory management: a memory manager saves kernel time, but not user time as far as I can tell. However, the problem I've noted affects user time. I've experimented with replacing various parts of the memory allocation and deallocation code with the FLINT memory manager, but it doesn't seem to affect user time (though naturally it cuts kernel time). 4) gcc compiler optimizations: I use -O3 -fexpensive-optimizations - funroll-loops Does anyone know of anything else? Are there other compiler optimizations I should use? Is there something else about memory management that I don't know? Is it to do with the way our library is linked? Does it have to do with MAGMA having root privileges because it was installed by root or something? There has to be a simple explanation for this. Bill Hart. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://sage.scipy.org/sage/ and http://modular.math.washington.edu/sage/ -~----------~----~----~----~------~----~------~--~---
