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

Ovanes, I wonder, though, is there a standard way to write integers to a stream_buf? As far as I can see, the ostreambuf_iterator takes character classes as template arguments, only. Regards, Roland Roland Bock wrote:

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 _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org mailto:Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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