This is a package that provides alternative pseudo-random number generators.

'''mt_rand()''' is based upon the Mersenne Twister PRNG algorithm ([http://www.math.keio.ac.jp/~matumoto/emt.html], [http://www.coyotegulch.com/algorithm/libcoyote/TwistedRoad/TwistedRoad.html]). This PRNG has an enormous period (in fact it is 2**19937-1 which is a Mersenne Prime, hence the name). It is also suposedly faster than the standard C library rand() function. Furthermore, while the stock Tcl rand function generates numbers in the range (0,1) - randmt produces numbers in the range [[0,1]]. If required, it can also produce values within (0,1) as well as integer values (any 32bit value) - we would just need some names for these functions.

'''isaac_rand()''' uses the ISAAC algorithm [http://www.burtleburtle.net/bob/rand/isaacafa.html] by Bob Jenkins. ISAAC (Indirection, Shift, Accumulate, Add, and Count) generates 32-bit random numbers. The period is guaranteed to be at least 2**40 and is 2**8295 on average. The results are uniformly distributed, unbiased, and unpredictable unless you know the seed. This PRNG '''is''' suitable for cryptographic use provided a suitably random seed can be provided.

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Currently the code is available at
 cvs -d:pserver:anonymous@cvs.tclsoap.sourceforge.net:/cvsroot/tclsoap co Random
and the distributable files are at http://sourceforge.net/projects/tclsoap in the downloads section.

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'''Usage'''

  # Seed and use the Mersenne Twister PRNG
  % expr {mt_srand(0)}
  0.548813502432
  % expr {mt_rand()}
  0.592844616527
  
  # Seed and use the ISAAC PRNG
  % expr {isaac_srand(0)}
  0.0943298905842
  % expr {isaac_rand()}
  0.187672290296
  
  # Extended ISAAC commands
  # Provide extra seed data (up to 256 values can be used)
  % ::isaac::isaac seed "\x01\x02\x03\x04\x05"
  
  # Get integers from the PRNG (must have been seeded already)
  % ::isaac::isaac integer
  1439929434
  
  # Get doubles (equivalent to the expr function)
  % ::isaac::isaac double
  0.960589176966

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[[ [Category Mathematics] | [Category Package] ]]