This has been known to unix developers for a long time, but there are no MS supplied development tools for NT that take advantage of this. On NT machines, we have noticed you can get around 15% faster builds (at least with our code) using -j2 on a single CPU, non hyperthreaded machine. Using -j3 cuts another 30-40% off the build time on a hyperthreaded machine. In fact, using number of CPU's (both real and hyperthreaded, or the product on SMP hyperthreaded machines) +1 seems to be about optimal. Unfortunately, the NT console doesn't deal well with multiple processes writing to it, so you may be able to read any errors that occur. And you can't redirect Jam's output from the compiler messages because as of MSVC 7.0, nothing is ever written to stderr. Probably best to use -d to turn off all of Jam's output and -q to keep Jam from continuing if there is an error. Then hope you aren't unlucky enough for more than one process to simultaneously have something say. But then you can't watch the progress. But then again writing server code on NT is always a compromise anyway.

Even on unix, Jam is superior to make in this area because Jam looks at everything as a whole. A make process, for example, could recurse into a subdirectory providing a dependency, all cpu's blazing, to take care of maybe one file while the entire build process waits for this. In Jam, the entire dependency tree is known ahead of time so all the cpu's are better tasked for the entire project. Sometimes you'll see different subprojects being built at the same time!

On Feb 13, 2004, at 12:11 AM, Alen Ladavac wrote: