Re: [Boost-users] Fastest way of serializing a huge vector of ints into a human readable string

1 Mar 2009

      Ovanes,

thanks for the explanation and the link.

I must admit that I avoided taking closer looks at stream_buf classes, 
but I will change that now :-)

Regards,

Roland

Ovanes Markarian wrote:
...
Roland that's not the fastest way with some other reagards, because 
stringstream as all iostream classes are designed to deal with thread 
safe apps and call lock/unlock pairs for _every_ character inserted. 
This operation is done by constructing the ostream::sentry guard. To be 
more efficient write your output to stream_buf classes.
try adapting this example to your needs:
http://codepad.org/ujfeLB72
When I did some tests, this brought me performance factor of 3 or 4 over 
common iostream.
With Kind Regards,
Ovanes
On Fri, Feb 27, 2009 at 6:46 PM, Roland Bock mailto:rbock@eudoxos.de> wrote:
Hi,
I have a program which produces a vector of integers (several
    million entries). I need to write that into a human-readable string
    of space separated numbers.
I wonder, what would be the fastest way?
My first attempt was
stringstream resultStream;
    copy(integers.begin(), integers.end(),
    ostream_iterator<int>(resultStream, " "));
    string result = resultStream.str();
But that requires copying the string.
Thus I was wondering if I could use boost to write to the target
    string directly?
boost::iostreams allow me to do the following:
string result;
    boost::iostreams::filtering_ostream
    out(boost::iostreams::back_inserter(result));
    copy(integers.begin(), integers.end(), ostream_iterator<uint64>(out,
    " "));
This is faster by almost a factor of 2.
Any ideas how to increase speed even more?
Thanks in advance,
Roland
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