[Beowulf] Win64 Clusters!!!!!!!!!!!!

Toon Moene toon at moene.indiv.nluug.nl
Sun Apr 8 13:30:41 EDT 2007


Jon Forrest wrote:

> One thing I've noticed about 64-bit computing in general
> is that it's being oversold. The **only** reason
> for running in 64-bit mode is if you need the additional
> address space.

I wouldn't be to sure of that.  Recently I became interested in the 
divisors of a given natural number.

The obvious Fortran program is:

       integer*8 n, i, j, k
       character*80 arg
       call getarg(1,arg)
       read(arg, '(i20)') n
       i = n
       j = 1
       k = i / j
       do while (k .ge. j)
          if (i .eq. k * j) print*, k, j
          j = j + 1
          k = i / j
       end do
       end

[ OK, this isn't purely Fortran 77, but close enough that
   most compilers will do the *right thing* ]

I tried it on 32 bit Linux (at work) and my laptop (AMD64 Linux), using 
gfortran 4.1.

The execution time difference was about 2 orders of magnitude.

-- 
Toon Moene - e-mail: toon at moene.indiv.nluug.nl - phone: +31 346 214290
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands
At home: http://moene.indiv.nluug.nl/~toon/
Who's working on GNU Fortran: 
http://gcc.gnu.org/ml/gcc/2007-01/msg00059.html
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