Re: gfortran, g95, and dual-core

Charles Russell <NOSPAM@xxxxxxxxxxxxx> wrote:

Can gfortran or g95 gain anything from dual- or multi-core processors in
either speed of compilation or speed of execution?

If nothing else, having a multiple cores allows mltiple processes to run
at the same time. This is, of course, an issue that has come up decades
ago with multi-processor archiertctures long before the current cop of
multi-core processors. Even on a single-use machine, you at least get
some benefit in that your program can get all of a core, while other
overhead stuff (such as the operating system and graphics user
interface) can use the other. That's overly simplified, just for
illustration of the idea.

Does anything
besides clock speeed matter much?

Um. Wow! That's a loaded question, and one that people spend whole
careers on. I think you just asked what matters in terms of program
performance. Perhaps you meant it in a more narrow sense. If so, I
missed it.

Many, many things matter. The details are complicated and vary widely as
a function of just about everything, probably including the phase of the
moon.

Today, many programs are limitted by memory bandwidth, which is
typically (mostly) independent of CPU clock speed. That's why cache is
such a big deal and spawns a large number of issues about taking best
advantage of cache.

Disk I/O can also be a big deal fo some programs (notably including
compilers). Sometimes using large amounts of memory can help lower disk
accesses to addres that issue.

And, of course, to pull out that old cliche - but one that is so true -
a good choice of algorithm usually matters more than anything else.

--
Richard Maine | Good judgement comes from experience;
email: last name at domain . net | experience comes from bad judgement.
domain: summertriangle | -- Mark Twain
.