-/*
- * Implementation of the Mersenne twister PRNG (pseudo random numer
- * generator). Implementation of MT19937. Has a period of 2^19937-1
- * which is a Mersenne Prime (hence the name).
- *
- * Implemented from specification and original paper:
- * http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/ARTICLES/mt.pdf
- *
- * This code is placed in the public domain by me personally
- * (Dale Weiler, a.k.a graphitemaster).
- */
-
-#define MT_SIZE 624
-#define MT_PERIOD 397
-#define MT_SPACE (MT_SIZE - MT_PERIOD)
-
-static uint32_t mt_state[MT_SIZE];
-static size_t mt_index = 0;
-
-static GMQCC_INLINE void mt_generate(void) {
- /*
- * The loop has been unrolled here: the original paper and implemenation
- * Called for the following code:
- * for (register unsigned i = 0; i < MT_SIZE; ++i) {
- * register uint32_t load;
- * load = (0x80000000 & mt_state[i]) // most significant 32nd bit
- * load |= (0x7FFFFFFF & mt_state[(i + 1) % MT_SIZE]) // least significant 31nd bit
- *
- * mt_state[i] = mt_state[(i + MT_PERIOD) % MT_SIZE] ^ (load >> 1);
- *
- * if (load & 1) mt_state[i] ^= 0x9908B0DF;
- * }
- *
- * This essentially is a waste: we have two modulus operations, and
- * a branch that is executed every iteration from [0, MT_SIZE).
- *
- * Please see: http://www.quadibloc.com/crypto/co4814.htm for more
- * information on how this clever trick works.
- */
- static const uint32_t matrix[2] = {
- 0x00000000,
- 0x9908B0Df
- };
- /*
- * This register gives up a little more speed by instructing the compiler
- * to force these into CPU registers (they're counters for indexing mt_state
- * which we can force the compiler to generate prefetch instructions for)
- */
- register uint32_t y;
- register uint32_t i;
-
- /*
- * Said loop has been unrolled for MT_SPACE (226 iterations), opposed
- * to [0, MT_SIZE) (634 iterations).
- */
- for (i = 0; i < MT_SPACE-1; ++i) {
- y = (0x80000000 & mt_state[i]) | (0x7FFFFFF & mt_state[i + 1]);
- mt_state[i] = mt_state[i + MT_PERIOD] ^ (y >> 1) ^ matrix[y & 1];
-
- i ++; /* loop unroll */
-
- y = (0x80000000 & mt_state[i]) | (0x7FFFFFF & mt_state[i + 1]);
- mt_state[i] = mt_state[i + MT_PERIOD] ^ (y >> 1) ^ matrix[y & 1];
- }
-
- /*
- * collapsing the walls unrolled (evenly dividing 396 [632-227 = 396
- * = 2*2*3*3*11])
- */
- i = MT_SPACE;
- while (i < MT_SIZE-2) {
- /*
- * We expand this 11 times .. manually, no macros are required
- * here. This all fits in the CPU cache.
- */
- y = (0x80000000 & mt_state[i]) | (0x7FFFFFFF & mt_state[i + 1]);
- mt_state[i] = mt_state[i - MT_SPACE] ^ (y >> 1) ^ matrix[y & 1];
- ++i;
- y = (0x80000000 & mt_state[i]) | (0x7FFFFFFF & mt_state[i + 1]);
- mt_state[i] = mt_state[i - MT_SPACE] ^ (y >> 1) ^ matrix[y & 1];
- ++i;
- y = (0x80000000 & mt_state[i]) | (0x7FFFFFFF & mt_state[i + 1]);
- mt_state[i] = mt_state[i - MT_SPACE] ^ (y >> 1) ^ matrix[y & 1];
- ++i;
- y = (0x80000000 & mt_state[i]) | (0x7FFFFFFF & mt_state[i + 1]);
- mt_state[i] = mt_state[i - MT_SPACE] ^ (y >> 1) ^ matrix[y & 1];
- ++i;
- y = (0x80000000 & mt_state[i]) | (0x7FFFFFFF & mt_state[i + 1]);
- mt_state[i] = mt_state[i - MT_SPACE] ^ (y >> 1) ^ matrix[y & 1];
- ++i;
- y = (0x80000000 & mt_state[i]) | (0x7FFFFFFF & mt_state[i + 1]);
- mt_state[i] = mt_state[i - MT_SPACE] ^ (y >> 1) ^ matrix[y & 1];
- ++i;
- y = (0x80000000 & mt_state[i]) | (0x7FFFFFFF & mt_state[i + 1]);
- mt_state[i] = mt_state[i - MT_SPACE] ^ (y >> 1) ^ matrix[y & 1];
- ++i;
- y = (0x80000000 & mt_state[i]) | (0x7FFFFFFF & mt_state[i + 1]);
- mt_state[i] = mt_state[i - MT_SPACE] ^ (y >> 1) ^ matrix[y & 1];
- ++i;
- y = (0x80000000 & mt_state[i]) | (0x7FFFFFFF & mt_state[i + 1]);
- mt_state[i] = mt_state[i - MT_SPACE] ^ (y >> 1) ^ matrix[y & 1];
- ++i;
- y = (0x80000000 & mt_state[i]) | (0x7FFFFFFF & mt_state[i + 1]);
- mt_state[i] = mt_state[i - MT_SPACE] ^ (y >> 1) ^ matrix[y & 1];
- ++i;
- y = (0x80000000 & mt_state[i]) | (0x7FFFFFFF & mt_state[i + 1]);
- mt_state[i] = mt_state[i - MT_SPACE] ^ (y >> 1) ^ matrix[y & 1];
- ++i;
- }
-
- /* i = mt_state[623] */
- y = (0x80000000 & mt_state[MT_SIZE - 1]) | (0x7FFFFFFF & mt_state[MT_SIZE - 1]);
- mt_state[MT_SIZE - 1] = mt_state[MT_PERIOD - 1] ^ (y >> 1) ^ matrix[y & 1];
-}