On Mon, Apr 16, 2012 at 2:29 PM, Christian Brabandt <[email protected]> wrote: > Hi Ben! > > On Mo, 16 Apr 2012, Ben Fritz wrote: > >> Eclipse has a "use optimal number of jobs" setting, but all this does >> is pass the -j flag with NO argument to make. Apparently this actually >> spawns ALL jobs which can be parallelized, all at once when make >> begins. Somehow on my and several coworkers' machines, this works just >> fine, and gives equivalent performance to the fastest time given from >> experimenting with various explicit numbers of jobs (which happened to >> be 1.5 times the number of processors for us...we all have 4-core >> machines). But...not passing an explicit number of jobs fails >> miserably on other machines, which more predictably run out of memory >> and/or process IDs and the build crashes. > > ,----[ http://www.gnu.org/software/make/manual/make.txt ]- > | If the `-j' option is followed by an integer, this is the number of > | recipes to execute at once; this is called the number of "job slots". > | If there is nothing looking like an integer after the `-j' option, > | there is no limit on the number of job slots. The default number of job > | slots is one, which means serial execution (one thing at a time). > `---- > > Well, "no limit on the number of job slots" doesn't sound right, in my > opinion. >
Yeah, it doesn't sound like it should work at all. Somehow though it works wonderfully on my 4-core machine, with equal performance to using 6 processes. Experiments trying 1-8 processes showed 6 as the magic number for my 4-core machine, and I had two coworkers verify it on theirs. It must be some magic in the scheduler on the 64-bit Windows XP system we all have, because another coworker with an older dual-core crashed 'make' every time he tried running without an explicit number of jobs. By the way, Eclipse showing "Optimal number of jobs" for the option name is even considered a bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=259768 I'm certainly not advocating using -j with no explicit number. I like the idea of this number being determined for me, though. I meant to give more weight to the "1.5 * number of CPUs seemed to work better for me" but re-reading what I wrote, I failed in that regard. -- You received this message from the "vim_use" maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php
