Use a different algorithm with the low entropy source for field trials.

third_party/mt19937ar/readme-mt.txt

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+This is a Mersenne Twister pseudorandom number generator
+with period 2^19937-1 with improved initialization scheme,
+modified on 2002/1/26 by Takuji Nishimura and Makoto Matsumoto. 
+
+Contents of this tar ball:
+readme-mt.txt	 this file
+mt19937ar.c	 the C source (ar: initialize by ARray)
+mt19937ar.out	 Test outputs of six types generators. 1000 for each
+
+1. Initialization
+  The initialization scheme for the previous versions of MT
+(e.g. 1999/10/28 version or earlier) has a tiny problem, that
+the most significant bits of the seed is not well reflected 
+to the state vector of MT.
+
+This version (2002/1/26) has two initialization schemes:
+init_genrand(seed) and init_by_array(init_key, key_length).
+
+init_genrand(seed) initializes the state vector by using
+one unsigned 32-bit integer "seed", which may be zero.
+
+init_by_array(init_key, key_length) initializes the state vector 
+by using an array init_key[] of unsigned 32-bit integers
+of length key_kength. If key_length is smaller than 624,
+then each array of 32-bit integers gives distinct initial
+state vector. This is useful if you want a larger seed space
+than 32-bit word.
+
+2. Generation
+After initialization, the following type of pseudorandom numbers
+are available. 
+
+genrand_int32() generates unsigned 32-bit integers.
+genrand_int31() generates unsigned 31-bit integers.
+genrand_real1() generates uniform real in [0,1] (32-bit resolution). 
+genrand_real2() generates uniform real in [0,1) (32-bit resolution). 
+genrand_real3() generates uniform real in (0,1) (32-bit resolution).
+genrand_res53() generates uniform real in [0,1) with 53-bit resolution.
+
+Note: the last five functions call the first one. 
+if you need more speed for these five functions, you may
+suppress the function call by copying genrand_int32() and
+replacing the last return(), following to these five functions.
+
+3. main()
+main() is an example to initialize with an array of length 4,
+then 1000 outputs of unsigned 32-bit integers, 
+then 1000 outputs of real [0,1) numbers. 
+
+4. The outputs
+The output of the mt19937ar.c is in the file mt19937ar.out.
+If you revise or translate the code, check the output
+by using this file. 
+
+5. Cryptography
+This generator is not cryptoraphically secure. 
+You need to use a one-way (or hash) function to obtain 
+a secure random sequence.
+
+6. Correspondence
+See:
+URL http://www.math.keio.ac.jp/matumoto/emt.html
+email matumoto@math.keio.ac.jp, nisimura@sci.kj.yamagata-u.ac.jp
+
+7. Reference
+M. Matsumoto and T. Nishimura,
+"Mersenne Twister: A 623-Dimensionally Equidistributed Uniform  
+Pseudo-Random Number Generator",
+ACM Transactions on Modeling and Computer Simulation,
+Vol. 8, No. 1, January 1998, pp 3--30.
+
+-------
+Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
+All rights reserved.