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An architecture:

Split your bigfile size across N machines.

Have a process on each machine that processes a filesize/N chunk of the bigfile. (Say, 32 machines each reading a different 32GB chunk of your 1TB file.)

Each reader accumulates word counts in a hash until the hash size approaches it's memory limit.

(Assume ~1.5GB/10 million words/keys on a 64-bit Perl; somewhat less on a 32-bit.)

When that limit is reached; it posts (probably udp) out the word/count pairs to the appropriate accumulator machines; frees the hash and continues reading the file from where it left off.

  • The file is only processed once.
  • It can be processed in parallel by as many reader processes/machines as your IO/Disk bandwidth will allow.
  • Each reader process only uses whatever amount of memory you decide is the limit.
  • You can split the accumulations across as many (or few) boxes as are required.
  • As only word/count pairs are exchanged, IO (other than reading the file) will be minimal.

No threading, shared memory or locking required. Simple to set up and efficient to process.


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In reply to Re^3: to thread or fork or ? by BrowserUk
in thread to thread or fork or ? by Anonymous Monk

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    [perldigious]: A question since I'm ignorant of what's normal for database management... Do admins change column names a lot in databases?
    [perldigious]: On occasion my scripts break, because they will do something that seems laregly pointless to me... like in this case, changing a column name from "ABC Category" to "ABC Category Override".
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