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

Subject: Re: [Boost-users] Fastest way of serializing a huge vector of ints into a human readable string
From: Roland Bock (rbock_at_[hidden])
Date: 2009-03-01 09:36:34

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 <rbock_at_[hidden] 
>> <mailto:rbock_at_[hidden]>> 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_at_[hidden] <mailto:Boost-users_at_[hidden]>
>>     http://lists.boost.org/mailman/listinfo.cgi/boost-users
>>
>>
>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> Boost-users mailing list
>> Boost-users_at_[hidden]
>> http://lists.boost.org/mailman/listinfo.cgi/boost-users
> _______________________________________________
> Boost-users mailing list
> Boost-users_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/boost-users