[Bug libstdc++/62237] New: ostream single character printing is slower than fprintf with "%c".

[mickey.veksler at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62237

            Bug ID: 62237
           Summary: ostream single character printing is slower than
                    fprintf with "%c".
           Product: gcc
           Version: 4.9.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mickey.veksler at gmail dot com

Created attachment 33383
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33383&action=edit
ostream vs. fprintf

I have tried to write a micro-benchmark to compare the performance of the
ostream and FILE interfaces. It turns out that GCC's ostream is performing
quite well except in one case:
out << ch;

It takes almost 2.5 times the wall-time of the fprintf(out, "%c", ch) version
(Please see the attached files). This does not make sense to me. Even worse,
the fprintf version takes only 60% CPU instead of the 99% of the fprintf
version.

In order not to make you follow my analysis, which is possibly wrong, I do not
add more of my results. I would say that from my analysis it seems that it
should be relatively easy to speed-up this case, significantly.