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- Xref: sparky comp.sys.super:871 comp.lang.fortran:2890
- Path: sparky!uunet!usc!sol.ctr.columbia.edu!emory!utkcs2!cupid.cs.utk.edu!eijkhout
- From: eijkhout@cupid.cs.utk.edu (Victor Eijkhout)
- Newsgroups: comp.sys.super,comp.lang.fortran
- Subject: Inner product / AXPY performance
- Message-ID: <l7gi3fINNmsd@utkcs2.cs.utk.edu>
- Date: 30 Jul 92 19:52:15 GMT
- Reply-To: eijkhout@cupid.cs.utk.edu (Victor Eijkhout)
- Organization: University of Tennessee, Knoxville - Department of Computer Science
- Lines: 23
- NNTP-Posting-Host: cupid.cs.utk.edu
-
- Yo hardcore number crunchers!
-
- I would like to get an idea of the difference in performance
- between inner products
-
- do i=1,n x = x + a(i)*b(i)
-
- and axpy operations
-
- do i=1,n x(i) = x(i) + a*b(i)
-
- which both have the same number of operations, but the inner product
- has an accumulation, which traditionally seems to be an
- unvectorizable idea.
-
- Please post if you know how your favourite vector processor / vector
- chip / Risc processor / whatever performs differently / the same
- on the two.
-
- My guess would be that the difference between these two operations
- can nowadays be conveniently neglected, but I might be wrong.
-
- Victor.
-