X-pop3-spooler: POP3MAIL 2.1.0 b 4 980420 -bs- Message-ID: <35CDB2C6.F3D49819@kali.com.cn> Date: Sun, 09 Aug 1998 22:31:34 +0800 From: Pan Xing X-Mailer: Mozilla 4.05 [en] (X11; I; Linux 2.0.30 i686) MIME-Version: 1.0 To: beastium-list AT Desk DOT nl Subject: Pgcc Slower than Gcc???(Not in mailist, re me diretly, Thx) Content-Type: text/plain; charset=gb2312 Content-Transfer-Encoding: 7bit Sender: Marc Lehmann Status: RO X-Status: A Content-Length: 3330 Lines: 84 Hi! Every One! I just plan to do some ting computation intensive work , ( wave simulation with PDE). A month ago, I have tested the gcc 2.7.2.3 under linux 2.0.30 in a PII233 box. Unfortunately, I found its performance is lower than MS's VC++5.0, it's about 63Mflops .vs. 70 Mflops. Tested with the wellknown flops.c (1992 version) I hear that Pgcc can deliver about 2-30% more power than gcc generally, So I tested it and gcc again this evening. My box is Pii233,64M, Slackware34/linux2.0.30, libc5.44. Test program: flops.c Version 2.0, 18 Dec 1992 by Al Aburto /* aburto AT nosc DOT mil */ Some weird things happened: 1) The flops.c compiled by gcc 2.7.2.3 WILL provide different results when runing under Xwindow's xterm and under ascii mode(I have installed kde, will it bother? ). RESULT under ASCII MODE: FLOPS C Program (Double Precision), V2.0 18 Dec 1992 Module Error RunTime MFLOPS (usec) 1 4.8490e-13 0.2787 50.2297 2 8.1272e-16 0.1322 52.9576 3 2.7316e-14 0.1612 105.4804 4 -3.8270e-15 0.1721 87.1572 5 -9.5745e-15 0.3926 73.8753 6 -1.2826e-14 0.2848 101.8108 7 1.2524e-10 0.4779 25.1116 8 -4.3365e-14 0.2938 102.1187 RESULT under Xterm FLOPS C Program (Double Precision), V2.0 18 Dec 1992 Module Error RunTime MFLOPS (usec) 1 -5.4193e-13 0.1605 87.2201 2 8.5760e-16 0.1334 52.4795 3 3.4567e-14 0.1615 105.2469 4 3.6970e-13 0.1737 86.3719 5 -5.1910e-15 0.3943 73.5532 6 2.3930e-14 0.2932 98.9196 7 -1.6524e-10 0.5447 22.0309 8 1.4631e-13 0.3033 98.9282 It seems that the result under Xterm is faster but the one under Ascii mode is more accurate. Why, I guess In Intel's chip only its internal parallism may affect its difference? Does any one who have meet similar situation or have experience with Intel 's Chip? Thanks in advance.! 2) The Pgcc is Rather Slower than Gcc!? a)I was surprised by the results. But it seems true. I use the pgcc-2.90.29 980515 (egcs-1.0.3 release), the result Pgcc .vs. Gcc is about 40M flops .vs. 60M flops. My pgcc doomed my machine! I read the Pgcc faq provided by http://www.gcc.ml.org, use all switches to accelarate which includ -O6, --funroll-all-loops -malign-double -mstack-align-double -marg-align-double -mpentium, All could not save me from the bad luck. I installed the pgcc as the readme and install reference in the package instructed me . ( patch, configure, make, make install under /usr/local/), What's wrong with it? I also got the comiled binary of pgcc2.90, no help. b) Some good news to be reported: under the pgcc the weird problem in 1) dispeared. the flops.c compiled by pgcc give identical results when running under X and Ascii mode. I know these questions may bother you. I am just new to gcc and come to the maillist first time. Oh! I am not hacker but waste so much time. God save me! Where is the devil?