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Remo Eichenberger
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 Posted: Sat Sep 13, 2003 11:48 pm Post subject: stringstream (binary) performance problem |
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(first sorry for my bad english)
i have a big performance problem with following (the file is 354KB):
my environment:
vc6 sp5
2.4 ghz P4
512 MB RAM
code:
fstream f("file",ios_base::in | ios_base::out | ios_base::binary);
stringstream ss;
ss << f.rdbuf();
this code use 6 seconds to finish !! this is very very slow.
i tryed many different methods:
1)
fstream f("file",ios_base::in | ios_base::out | ios_base::binary);
istream::pos_type size = stream_size(f);
string buffer;
buffer.reserve(size);
istream_iterator
copy(f_iter, istream_iterator<char>(),buffer.begin());
this use 0.057 seconds
2)
fstream f("file",ios_base::in | ios_base::out | ios_base::binary);
vector<char> buffer;
istream_iterator<char> f_iter(f);
copy(f_iter, istream_iterator<char>(),back_insert_iterator< vector
this use 0.072
3) the fastest
fstream f("file",ios_base::in | ios_base::out | ios_base::binary);
istream::pos_type size = stream_size(f);
char* buffer = new char[size];
f.read(buffer,size);
delete [] buffer;
this use 0.007 seconds.
i found that the performance problem is the minimum allocation-size in the
implementation of basic_streambuf from Dinkumware. This is 32 byte !? when i
use a my patched streambuf (65535) and insert this in the stringstream then
the first example use 0.055 second !
my question:
1) what is the "correct" and "stl-like" way to solve this performance
problem without changing the interface of the sstream ? ( i don't wan't use
static array c-style)
2) is the following code correct to inject the patched streambuf ?
basic_stringbufx< char, char_traits strbufx;
stringstream ss;
ss.ostream::rdbuf(&strbufx);
ss << f.rdbuf();
thanks for your input
Remo Eichenberger
btw. the vc7.1 - compiler optimize the first sample and has 0.01 second !!
:-)
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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White Wolf
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| Posted: Sun Sep 14, 2003 1:41 am Post subject: Re: stringstream (binary) performance problem |
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Remo Eichenberger wrote:
| Quote: | (first sorry for my bad english)
i have a big performance problem with following (the file is 354KB):
my environment:
vc6 sp5
2.4 ghz P4
512 MB RAM
code:
fstream f("file",ios_base::in | ios_base::out | ios_base::binary);
stringstream ss;
ss << f.rdbuf();
this code use 6 seconds to finish !! this is very very slow.
[SNIP]
1) what is the "correct" and "stl-like" way to solve this performance
problem without changing the interface of the sstream ? ( i don't
wan't use static array c-style)
|
IMO first is to go to the Dinkumware site and check out if your header is
patched:
http://www.dinkumware.com/vc_fixes.html
Look for fstream and see the fix for a _performance_ issue. It might be the
thing you are looking for.
I think it is worth to read through that page (if you still have to use a
compiler from the previous millenia  ) and apply those fixes which might
matter.
--
WW aka Attila
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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Stephen Howe
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| Posted: Sun Sep 14, 2003 11:23 am Post subject: Re: stringstream (binary) performance problem |
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| Quote: | this code use 6 seconds to finish !! this is very very slow.
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I think your basic problem is the slow stringstream. Go to
http://www.dinkumware.com/vc_fixes.html
and apply the sstream patch (and apply the others).
Note: These patches never made it into any of Microsoft's SP's for VC++ 6.0
For VC++ 7.1, Microsoft have had a change of policy and any fixes to
Dinkumware's files will be in SP's for 7.1.
That is better news for C++ programmers using this compiler.
Stephen Howe
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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Ulrich Eckhardt
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| Posted: Sun Sep 14, 2003 11:24 am Post subject: Re: stringstream (binary) performance problem |
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Remo Eichenberger wrote:
[bad performance of VC6's native stringstreams]
Try switching to STLport([url]www.stlport.org)[/url], it is free and much more
performant, and it has an active forum where you can get help with
problems.
See also the thread "how do i create a ostringstream with pre-allocated
memory buffer", it also offers a possible solution to your problem.
Uli
--
Questions ?
see C++-FAQ Lite: http://parashift.com/c++-faq-lite/ first !
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Francis Glassborow
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| Posted: Sun Sep 14, 2003 1:33 pm Post subject: Re: stringstream (binary) performance problem |
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In article <3f63f2a0$0$272$cc9e4d1f (AT) news (DOT) dial.pipex.com>, Stephen Howe
<NOSPAMsjhowe (AT) dial (DOT) pipex.com> writes
| Quote: | I think your basic problem is the slow stringstream. Go to
http://www.dinkumware.com/vc_fixes.html
and apply the sstream patch (and apply the others).
Note: These patches never made it into any of Microsoft's SP's for VC++ 6.0
For VC++ 7.1, Microsoft have had a change of policy and any fixes to
Dinkumware's files will be in SP's for 7.1.
That is better news for C++ programmers using this compiler.
|
You imply that the failure to provide updates to the Library files was a
matter of policy. I am all in favour of placing blame on implementors
when they deserve it but as I understand it neither Dinkumware nor
Microsoft were responsible for the failure to include updates to the
library in VC++ 6.0. For most of the period covered by VC++ 6.0 there
was legal action involving Dinkumware but not MS one consequence of
which was that Dinkumware was prohibited from licensing updates for
redistribution. MS was an innocent bystander.
--
Francis Glassborow ACCU
64 Southfield Rd
Oxford OX4 1PA +44(0)1865 246490
All opinions are mine and do not represent those of any organisation
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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Remo Eichenberger
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| Posted: Wed Sep 17, 2003 9:43 am Post subject: Re: stringstream (binary) performance problem |
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"White Wolf" <wolof (AT) freemail (DOT) hu> wrote
| Quote: | Remo Eichenberger wrote:
(first sorry for my bad english)
i have a big performance problem with following (the file is 354KB):
my environment:
vc6 sp5
2.4 ghz P4
512 MB RAM
code:
fstream f("file",ios_base::in | ios_base::out | ios_base::binary);
stringstream ss;
ss << f.rdbuf();
this code use 6 seconds to finish !! this is very very slow.
[SNIP]
1) what is the "correct" and "stl-like" way to solve this performance
problem without changing the interface of the sstream ? ( i don't
wan't use static array c-style)
IMO first is to go to the Dinkumware site and check out if your header is
patched:
http://www.dinkumware.com/vc_fixes.html
Look for fstream and see the fix for a _performance_ issue. It might be the
thing you are looking for.
I think it is worth to read through that page (if you still have to use a
compiler from the previous millenia ) and apply those fixes which might
matter.
|
hi
thanks for info, but i have allready tryed the newest dinkumware-stl for vc6
(3.0 . but this don't fix the problem. i found another performance problem
in ostream<<(streambuf*). this use sgetc/sputc and not sgetn/sputn.
Remo
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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