It dawned on me there is another way to collect the output from the threads. You can open a filehandle in the main thread, pass it's fileno to the thread, then let the thread write to the dup'd filehandle. See [threads] Open a file in one thread and allow others to write to it for the technique.

Anyways, you could open 1 filehandle for each thread, for that thread to report results back to the main thread. Pass the fileno of that filehandle to each thread at creation time. In the main thread, setup an IO::Select object to watch all the filehandles. Have the main thread open a private filehandle for the final output file, and as IO::Select reads the various data from each thread, it writes the output to the output file.

This would allow the threads to write without worrying about locking, while the main thread's select loop would actually handle the writing, and possibly sorting, the data out to file.

I don't know how it would work speedwise, as select will block if one thread reports alot of data, but this might be minimized by using large filehandle buffers.

That is what I would try first.

I'm not really a human, but I play one on earth.
Old Perl Programmer Haiku ................... flash japh

In reply to Re^3: how to split huge file reading into multiple threads by zentara
in thread how to split huge file reading into multiple threads by sagarika

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