Support Programs

The following programs provide support for testing and performance assessment.

rand-src: Generate random message bits.
rand-src source-file seed n-bits

Creates a file of random messages bits called source-file, which is suitable for testing the correctness and performance of other programs. The bits in the file are independent, and are equally likely to be 0 or 1. They are generated pseudo-randomly based on seed. The actual random number seed used will be seed times 10 plus 2, so that the stream of pseudo-random numbers will not be the same as any that might have been used by another program.

The n-bits argument specifies the number of bits to produce. It can be a single number, or it can consist of a block size and a number of blocks, written with x separating these numbers, with no spaces. Each block is written as a single line, with the bits in the block represented by the characters "0" and "1", with no intervening spaces. If the bit count is given by a single number, the block size is assumed to be one.

Example: The following command produces a file containing 3 blocks, each consisting of 15 random bits, produced using the pseudo-random number strean identified by the seed of 17:

The contents of the file rsrc after this command might be something like the following:

verify: Verify that decoded blocks are codewords, and that they match the source.
verify [ -t ] pchk-file decoded-file [ gen-file [ source-file ] ]

Checks whether or not the blocks in decoded-file are codewords, according to the parity check matrix in pchk-file. If gen-file is specified, the message bits of the blocks are also checked against the corresponding blocks of source-file, or against zero if source-file is not given. (Normally, one would leave out source-file only if the transmit command was used with an argument specifying that zeros are to be transmitted, rather than a file of encoded data.)

A summary of the results is displayed on standard error, including the total numbers of blocks and the number with one or more parity check errors. If a gen-file was specified, the number of blocks with one or more source errors and the number with one or more errors of both kinds are also displayed, and a second line is displayed giving the bit error rate from comparing the decoded message bits with the true message bits (zeros if no source file was given).

If the -t option is given, block-by-block results are printed on standard output in two or three columns, giving the block number (from zero), the number of parity check errors for that block, and the number of errors in source bits. The last column is omitted if gen-file is not specified. The columns are preceded by a line of headers, so the file is suitable for reading into the S-Plus or R statistics packages, with a command such as

data <- read.table(file,header=T)

Warning messages are displayed on standard error if the number of bits in decoded-file is not a multiple of the block length, or if source-file is too short. Newlines in these files are ignored, even though they would normally occur at the ends of blocks.

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