[Bug libstdc++/45574] ifstream::getline() is extremely slow

["tstarling at wikimedia dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #9 from tstarling at wikimedia dot org  2010-09-08 02:36 -------
Created an attachment (id=21732)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21732&action=view)
100000 lines, 500 bytes per line

Test file attached as requested, compressed with gzip. Test code follows.

getline-test.cpp

#include <iostream>

int main(int argc, char** argv) {
        char buffer[65536];
        while (std::cin.getline(buffer, sizeof(buffer), '\n'));
        return 0;
}

fgets-test.cpp:

#include <stdio.h>

int main(int argc, char** argv) {
        char buffer[65536];
        while (fgets(buffer, sizeof(buffer), stdin));
        return 0;
}

$ time ./fgets-test < 500x100k.txt

real    0m0.076s
user    0m0.040s
sys     0m0.032s

$ time ./getline-test < 500x100k.txt

real    0m2.727s
user    0m2.672s
sys     0m0.028s


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45574