Re: gfortran, g95, and dual-core

Tim Prince wrote:
Charles Russell wrote:
Can gfortran or g95 gain anything from dual- or multi-core processors in
either speed of compilation or speed of execution? Does anything
besides clock speeed matter much?
gfortran, since 4.2, supports OpenMP parallel compilation (but
apparently not for mingw). make -j can give a big jump in build
performance, worth doing even if you are a Windows fanatic.

The gnu make info file in my Cygwin distribution says that option -j is ineffective with MS-DOS. Does it do anything under Cygwin? What factor is a "big jump?"

Not sure what you have in mind when you say "anything."

I should have been more specific. First of all, I'm a scientific user, not a programmer, so that most of your response is beyond my understanding. Since the first IBM PC, I've been accustomed to an order-of-magnitude speed gain every time I replaced a computer, normally about every 4 years, alternating between a minimal laptop and an upper midrange desktop, so that one or the other was always less than 2 years old. Two years ago was the laptop's turn, and I got the expected order-of-magnitude gain. Now it is the desktop's turn, but my 4.5-year-old desktop has a clock speed of 2.4 GHz, and even the top range Intel chips are hardly any faster now. Instead, they have gone to dual-core. Perhaps the market is all in laptops, so that high-speed high-power chips are out of fashion.

What matters to me is not only execution speed, though that is important, but also compilation speed, since my "user interface" is to edit the source code. With annually increasing clock speeds, I was getting both. The heavy lifting in my code is done with netlib routines, so I simply want old code to run faster. The gain must be more than a factor of 2 or 3 to matter much. I had come to expect that much gain every couple of years.

Can I gain anything by replacing my old PC? If so, what are the critical specifications when buying a mid-price-range PC for crunching numbers with fortran?

My original question was more general because I was also curious how serious fortran programmers expect to deal with the changing trend in chip development, but the answers are Greek to me.


Recent linux
distros do an improved job of default scheduling on multi-core, often
relieving you from fiddling with taskset and the like.
> Windows fanatics
rely on low level affinity calls, not what I like to do with Fortran.
Quad cores with the lowest available buss speeds saturate quickly on
memory operations with parallel programming. The buss clock speed is
more important then than the CPU clock speed.
.

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