Re: IVF 10: IO speed slower with full optimizations than with a debug build
- From: Al Greynolds <awgreynolds@xxxxxxxxxxxxx>
- Date: Thu, 20 Sep 2007 14:54:09 -0700
On Sep 20, 10:48 am, Al Greynolds <awgreyno...@xxxxxxxxxxxxx> wrote:
Thought I'd ask here first (before going to Intel) to see if anybody
has seen this odd behavior with IVF 10.0. I create a fully optimized
verision of my application with:
/QxN /O3 /Qipo /Qprec-div- /Qprec-sqrt- /fp:fast=2 /Qparallel /
Qcomplex-limited-range /Qopenmp
I also create a separate debug version with:
/traceback /QxW /CU /Qtrapuv /CB /Od
As expected most operations in the application run significantly
faster with the optimized version. However, one operation dominated
by READing a large file is actually 2x SLOWER on the the optimized
version than on the debug version.
Anybody got any ideas what could be going on here? One thing, I've
always noticed the IVF's file IO is much slower than Lahey's LF95 (IVF
is faster in everything else).
Al Greynoldswww.ruda.com
Here's a test program and timings:
program iospeed
character(1836) line !some files can have lines this long
call getarg(1,line)
open(1,file=trim(line),action='read',status='old')
m=0; n=0
do
! read(1,'(q,a)',iostat=i) l,line(:l); if (i/=0) exit !non-standard
version
read(1,'(a)',iostat=i) line; if (i/=0) exit; l=len_trim(line) !
standard
m=max(l,m); n=n+1
enddo
close(1)
write(*,*) n,m
end
Elapsed times in seconds on a 150MB file (3 million lines up 73
characters long)
Optimimzed Debug
Non-standard 10.9 3.1
Standard 23.2 14.9
.
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