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From: daniel.lemire@nrc.gc.ca To: gcc-gnats@gcc.gnu.org Subject: libstdc++/10672: Binary IO with fstream is slow in 3.2+ compared to gcc 2.96 Date: Thu, 08 May 2003 00:46:00 -0000 [thread overview] Message-ID: <20030508004557.14047.qmail@sources.redhat.com> (raw) >Number: 10672 >Category: libstdc++ >Synopsis: Binary IO with fstream is slow in 3.2+ compared to gcc 2.96 >Confidential: no >Severity: serious >Priority: medium >Responsible: unassigned >State: open >Class: sw-bug >Submitter-Id: net >Arrival-Date: Thu May 08 00:45:59 UTC 2003 >Closed-Date: >Last-Modified: >Originator: daniel.lemire@nrc.gc.ca >Release: gcc version 3.4 20030507 (experimental) + gcc version 3.2.3 >Organization: >Environment: linux 2.4.18-3 (RedHat 7.3) on 686 >Description: fstream in 3.x series is extremely slow for binary files compared to pre-3.x. latest CVS (20030507) real 0m4.773s user 0m1.680s sys 0m3.010s 3.2.3 (release) real 0m5.503s user 0m2.710s sys 0m2.790s gcc 2.96 (Clearly better) real 0m2.920s user 0m1.090s sys 0m1.830s Of course, this was one trial on the same machine. I have more complex software here where the drop in speed is as high as 5 times. This is a show stopper for me. (This is related to bug 8761 but this bug is specific to binary files and thus doesn't involve formatting issues.) >How-To-Repeat: given the file test.cpp below =================== #include <fstream> using namespace std; int main() { fstream s("test.bin",ios::binary | ios::in | ios::out); for (int i = 0; i < 300000;i++) { s.seekp(0); s.write((char *) & i, sizeof(int)); s.seekp(sizeof(int)); s.write((char *) & i, sizeof(int)); } return 0; } =============== do g++ -o a.out test.cpp -O2 followed by time ./a.out >Fix: Revert back to gcc 2.96. >Release-Note: >Audit-Trail: >Unformatted:
next reply other threads:[~2003-05-08 0:46 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2003-05-08 0:46 daniel.lemire [this message] 2003-05-18 8:26 paolo
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