Re: [Quickfix-developers] Details for Solaris / SunPRO 5.3 build

[Caleb E. <cal...@gm...>]

On Tue, 13 Jul 2004 13:54:50 -0500, Oren Miller <or...@qu...> wrote:

> I noticed you replaced some sprintf calls with ostringstreams.  We
> actually used to do this, but performance testing revealed that the
> sprintf calls were considerably faster.  I don't remember the exact
> numbers, but I believe using the sprintf calls made message
> construction something on the order of 10% faster.  That's pretty
> significant.  Is there a particular reason you changed these?

     On Linux I've definitely found this to be the case.  Using
sprintf to do the formatting and just sending char*'s to the iostreams
is considerably faster.  You can optimize even further by collecting
the return value of sprintf and using ostream::write (const char*,
streamsize) instead of ostream::operator<<, which will avoid at least
a strlen call.  Taken together, I think these will give you a good
deal more than a 10% performance improvement.

     I think there is some additional optimization that could be done
inside the QF Field class by reserving an appropriate amount of
storage for m_data in the setString method before assigning to it.  We
have found std::string::append to be a bottleneck when doing this sort
of thing on Linux.  It would have to be a bit of a guesstimate though,
since you don't know the number of digits in the ASCII representation
of the tag.

-- 
Caleb Epstein
cal...@gm...