Re: About Migrating from F77 to F95
- From: Tim Prince <timothyprince@xxxxxxxxxxxxx>
- Date: Mon, 30 Apr 2007 06:30:14 -0700
zuying@xxxxxxxxx wrote:
Hi all,
I used to write f77 codes and now I want to migrate to f95. Since
there is a large set of old f77 styled codes in my own lib, I have
several questions on the necessities for the migration:
1. if I keep the old codes unchanged and only re-compile them with
compilers like ifort, will the efficiency be promoted a lot even
without rewriting codes? and in what degree the efficiency will be
promoted if I further rewrite all the codes in f95 style and recompile
them with ifort?
As others said, you ask for a comparison between an unknown compiler and an unknown version of ifort, so no answer makes much sense. ifort, particularly in the latest versions, is exceptionally good at vectorizing loops with many assignments, provided they meet the qualifications. It also necessarily works harder at vectorizing double precision than certain other compilers.
ifort will gain efficiency from modern syntax only in those cases where your rewrite forces you to make better optimizable source code. ifort for 32-bit and 32-bit extended 64-bit depends heavily on vectorization of stride 1 arrays as its primary means for optimization. ifort still tends to be weak in optimization of array syntax with non-default stride.
ifort is just beginning to address the issues of fusion for efficiency for the recent CPUs which care about it. So, you might not gain as much from such a move if you don't intend to keep your compiler up to date.
gfortran is doing well in optimization of f95 syntax, short of dealing with fusion and the like.
.
- References:
- About Migrating from F77 to F95
- From: zuying@xxxxxxxxx
- About Migrating from F77 to F95
- Prev by Date: Re: Fortran DINT help
- Next by Date: Question about KIND
- Previous by thread: Re: About Migrating from F77 to F95
- Next by thread: Question about KIND
- Index(es):
Relevant Pages
|
|
