Inside Intel's $20M Multicore Research Program

An anonymous reader writes "You may have heard about Intel's and Microsoft's efforts to finally get multi-core programming into gear so that there actually will be a developer who can program all those fancy new multicore processors, which may have dozens of core on one chip within a few years. TG Daily has an interesting article about the project, written by one of the researchers. It looks like there is a lot of excitement around the opportunity to create a new generation of development tools. Let's hope that we will soon see software that can exploit those 16+core babies. 'The problem of multi-core programming is staring at us right now. I am not sure what Intel's and Microsoft's expectations are, but it is quite possible that they are in fact looking at fundamental results from the academic centers to leverage their large work force to polish and realize the ideas that come forth. It calls for a much closer collaboration between the centers and the companies than it appears at first sight.'"

Comments

Re:stupid much?

[Jerry Coffin]

Instead of trying to convince everyone on Earth to change all existing software, why doesn't Microsoft just make the next version of Windows have a process handler that can process single threads on multiple cores at once? Actually technically I think Intel could do that internally on their processors too sort of like RAID for cores.

Intel's been doing that (to some degree) since the Pentium, and they increased it a lot in the Pentium Pro/Pentium II. It works reasonably well up to a point (modern chips typically execute an average of two instructions per clock cycle) but definitely has limits.

Compilers to automatically detect when instructions can be executed in parallel have been around for years. Cray had vectorizing compilers by the late 1970's, and within rather specific limits, they worked perfectly well. Just for example, if you wrote a loop like:

for (int i=0; i<256; i++)
a[i] = b[i] * c[i];

they'd break the loop down into four actual executions of a loop, each of which worked on 64 items in parallel. It had independent execution units, so at a given time it'd normally be loading one set of 64 items into one set of registers, executing multiplications on a second set of 64 items, and storing results from a third set of 64 registers.

That has a couple of problems though. First of all, if you're not careful, it's pretty easy to create loops with (apparent) dependencies from one iteration to the next, so the compiler can't parallelize the code. Second, this works well for vector processors, but probably not nearly so well for a large number of completely independent processors (which have higher communication overhead, meaning that starting up things to happen in parallel is more expensive).

If you're willing to provide the compiler with a little help, it can do quite a bit more, such as with MPI. The standard MPI interface is pretty low-level, but if you want to do the job in C++, Boost.MPI helps out quite a bit (cheap plug: if you want to know more, consider attending Boostcon '08).