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I've got a quad core Intel processor. I've got a big file split into little ones as RAR files, foo.r00, foo.r01, etc. which the RAR program extracts into one file/directory. Is there a RAR program that I can specify like "use four cores" in the extract process? At the moment it sits there using 100% of one core. I recognise the bottleneck might be my hard drive anyway, but I don't see a lot of HD usage and suspect the decompression process is more intensive than waiting on I/O.

For example, GNU Make accepts a (-j, I think) argument to tell it how many cores to use, which I used to compile PHP 6 really quickly.

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3 Answers

up vote 7 down vote accepted

http://www.7-zip.org/ supports multi-threading, but you'll probably be HDD bottle necked.

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I know 7-Zip supports multiple threads, but I believe it only supports up to 2 threads, and then only when compressing. Most compression algorithms (RAR included I am sure) are optimized for fast decompression, so most likely you are throttled by the disk I/O. Additionally RAR is a solid archive, making it a single data block internally, so you cannot decompress individual chunks separately (since there is only one).

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Solid archive is an option, default off. And how is that relevant to this question? –  Pyrolistical Aug 7 '09 at 0:26
    
To divide decompression between threads you would need to give each thread its own data block. With a solid archive there can be only one data block. If solid is off then it might be an option. –  Jim McKeeth Aug 7 '09 at 0:30
    
Its not that simple. You might still be able to use multiple threads. It really depends on the data format. –  Pyrolistical Aug 7 '09 at 0:33
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Just in case someone is searching and comes across this. Winrar now uses multiple cores to compress and decompress RARs also the person above me is wrong on his explanation of why it wouldn't have been capable of being multi-threaded.

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