The problem is the size of the file is large(About 800Mb to 2Gb)
Repeating what was discussed in the CB, tye maintains Algorithm::Diff so he'd be your best bet for issues related to the module.

With such large files though, you may need to change your approach. Assuming that Algorithm::Diff is bogging down due to the large file size, the idea is that you should make sure that not so much of the data is loaded at one time.

Method 1

Algorithm::Diff works from two arrays, right? If so perhaps the easiest thing to do is just to pass it (references to) two Tie::File objects.

Update: well, it's not that simple. Algorithm::Diff builds a hash to keep track of indexes, which grows (O(?)) with the length of the arrays passed.

Method 2

If that didn't work (or was too slow) I'd do something like this (pseudocode):

  declare @differences
  open file1 and file2
  read chunk1 from file1 (64mbyte)
  read chunk2 from file2 (64mbyte)
  while (chunk1 contains data)
    compute h1: md5hex of chunk1
    compute h2: md5hex of chunk2  
    if h1 != h2
      compute @diff: pass chunk1 and chunk2 to Algorithm::Diff
      append @diff to @differences
    end-of-if
    read chunk1 from file1 (64mbyte)
    read chunk2 from file2 (64mbyte)
  end-of-while
  close file1 and file2
  #maybe combine adjacent deltas in @differences (eg: by line number) 
  report @differences

[download]
That way Algorithm::Diff only ever deals with 2x 64Mbyte of data at a time. If two adjacent chunks both contain differences between the files, you might investigate whether there's some way to combine those differences.

-David

In reply to Re: Text difference by erroneousBollock
in thread Text difference by Eye beauty

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