QTextStream to console: endl and flush slow down program considerably?



  • This is mainly curiosity, but it appears that
    @
    QTextStream out(stdout);
    out << "Test.\n"; // fast, does not flush (delayed output on console)
    out << "Test." << endl; //slow, flushes and appends a newline
    out << "Test.\n" << flush; //slow as above
    @

    "Fast" being ~2.1 seconds, "slow" being ~3 seconds for a list of 6000 files. I'm guessing this has something to do with the << operator and what's going on "behind the scenes".

    Question is, how do I display the message without slowing down the output?
    Is there a better (=faster) way to print non-debug messages for the user?
    Should I just make a --verbose switch in case the user wants to see the output?



  • Hi,

    You can look at Qt's source if your curious enough.

    If you really want "fast", I suggest you use <stdio.h> API's. If you do so, make sure that you convert QString's to appropriately encoded char arrays.



  • In my tests using QTextStream without flushing is about as fast as stdio.h APIs, so I think I'll just use that. Thanks for the reply.


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