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J.S. Leon's webpage

Goals

• Fix up Leon's code for modern use.

Progress

• Fixed several issues relating to outdated design.
  • Originally defaulted to using short's: now uses unsigned's.
  • Changed obsolete CLK_TCK to CLOCKS_PER_SEC.
• Discovered a serious fencepost error in loops.
  • Temporary solution: allocate one more memory spot than necessary to allow Leon's indexing
  • Long term: correct all of Leon's loops to index properly.
• Discovered undocumented restriction on Cayley library names: no hyphens.

Solutions to known bugs

1. Related to reading the input file:

   • ./wtdist huffman-code4.gap 6 huffman-matrix4 // seems to work, creates huffman-matrix4 file
     ./desauto -code huffman-code4.gap huffman-matrix4 huffman-autgp4 // does not work
     
     output:
     Error: Library block huffman-matrix4 not found in specified library.
     Program was executing function read01Matrix (line 234 in file
     ../../src/leon/src/readdes.c).

   • Related files:

     • huffman-code4.gap

   • SOLUTION: Cayley library format does not support names with hyphens. Use only alphanumeric and underscore characters.
2. Bus Errors

   • ./wtdist example1::left 4 really
     Bus error

   • Related file:

     • example1

   • Happens on OS X, but not Linux- it is due to invalid memory access.
   • SOLUTION: see above, regarding "fencepost error."

Known Bugs in Leon

1. Running out of memory:
   • W. C. Huffman describes a general procedure to produce examples of this bug:

     The main problem always seems to be when there are only a few minimal weight codewords.  I think you can create a lot of examples that will make it difficult in the following way: Let C1 be any code you want with minimum weight at least 3. Let C2 be the [2,1,2] code with basis [1 1].  Form the direct sum of C1 and C2.  This will create a code of minimum weight 2 with only one codeword of minimum weight 2.  I have a feeling this will give you trouble even if the code C1 has an automorphism group that is easy to compute.

   • The following codes, as noted by Huffman, commonly cause an out of memory condition. Even if this doesn't happen, they are still good benchmarks for memory use:

     Example 1:
     1111111111110000000000001100000000
     0000000000001010100000000010101011
     0000000000000101010000000001010111
     0000000000000000001010100000001110
     0000000000000000000101010000001101
     0000001010101010100000001000100000
     0000000101010101010000000100010000
     1010100000001010100000001010000000
     0101010000000101010000000101000000
     0010100000000010100011110000000000
     0001010000000001010011110000000000
     1000100000001000101100110000000000
     0100010000000100011100110000000000
     0000000010100011110010100000000000
     0000000001010011110001010000000000
     0000001000101100111000100000000000
     0000000100011100110100010000000000
     
     Example 2:
     1111111111110000000000001100000000
     0000000000001010100000000010101011
     0000000000000101010000000001010111
     0000000000000000001010100000001110
     0000000000000000000101010000001101
     0000001010101010100000001000100000
     0000000101010101010000000100010000
     1010100000001010100000001010000000
     0101010000000101010000000101000000
     0010100000000010100011110000000000
     0001010000000001010011110000000000
     1000100000001000101100110000000000
     0100010000000100011100110000000000
     0000000010100011110001010000000000
     0000000001010011110010100000000000
     0000001000101100110100010000000000
     0000000100011100111000100000000000
     
     Example 3:
     1111111111110000000000001100000000
     0000000000000000001111110010101010
     0000000000000000001111110001010101
     0000000000001010101010100000000011
     0000000000000101010101010000000011
     0000001010100000000000001000101000
     0000000101010000000000000100010100
     1010100000000000000000001010001000
     0101010000000000000000000101000100
     0010100000000010100011110000000000
     0001010000000001010011110000000000
     1000100000001000101100110000000000
     0100010000000100011100110000000000
     0000000010100011110010100000000000
     0000000001010011110001010000000000
     0000001000101100111000100000000000
     0000000100011100110100010000000000
     
     Example 4:
     1111111111110000000000001100000000
     0000000000000000001111110010101010
     0000000000000000001111110001010101
     0000000000001010101010100000000011
     0000000000000101010101010000000011
     0000001010100000000000001000101000
     0000000101010000000000000100010100
     1010100000000000000000001010001000
     0101010000000000000000000101000100
     0010100000000001010011110000000000
     0001010000000010100011110000000000
     1000100000000100011100110000000000
     0100010000001000101100110000000000
     0000000010100011110001010000000000
     0000000001010011110010100000000000
     0000001000101100110100010000000000
     0000000100011100111000100000000000

2. Infinite Hangs (?)
   • These have not yet been tested...

     checking equivalence of:
     
     [1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
     [0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1]
     [0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1]
     [0 0 1 1 1 1 1 1 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1]
     -----------------------------------------------------------------
     [1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
     [0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1]
     [0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1]
     [0 0 1 1 0 0 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1]
     
     
     checking equivalence of:
     
     [1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
     [0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
     [0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1]
     [0 0 1 1 0 0 1 1 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1]
     -----------------------------------------------------------------
     [1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
     [0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
     [0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1]
     [0 0 1 1 0 0 1 1 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1]

   • This example also leads to an infinite loop in computeSubgroup...

     ./wtdist huffman-code4.gap 6 huffman_matrix4 // now works, using underscores
     ./desauto -code huffman-code4.gap huffman_matrix4 huffman_autgp4 // fall into infinite loop

   • Related files:

     • huffman-code4.gap

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