mirror of https://github.com/skeeto/pixelcity.git
94 lines
2.9 KiB
C++
94 lines
2.9 KiB
C++
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/*-----------------------------------------------------------------------------
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r a n d o m
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-----------------------------------------------------------------------------*/
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/*-----------------------------------------------------------------------------
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The Mersenne Twister by Matsumoto and Nishimura <matumoto@math.keio.ac.jp>.
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It sets new standards for the period, quality and speed of random number
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generators. The incredible period is 2^19937 - 1, a number with about 6000
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digits; the 32-bit random numbers exhibit best possible equidistribution
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properties in dimensions up to 623; and it's fast, very fast.
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-----------------------------------------------------------------------------*/
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#define LOWER_MASK 0x7fffffff
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#define M 397
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#define MATRIX_A 0x9908b0df
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#define N 624
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#define TEMPERING_MASK_B 0x9d2c5680
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#define TEMPERING_MASK_C 0xefc60000
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#define TEMPERING_SHIFT_L(y) (y >> 18)
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#define TEMPERING_SHIFT_S(y) (y << 7)
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#define TEMPERING_SHIFT_T(y) (y << 15)
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#define TEMPERING_SHIFT_U(y) (y >> 11)
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#define UPPER_MASK 0x80000000
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#include <memory.h>
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#include "random.h"
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static int k = 1;
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static unsigned long mag01[2] = {0x0, MATRIX_A};
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static unsigned long ptgfsr[N];
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/*-----------------------------------------------------------------------------
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-----------------------------------------------------------------------------*/
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unsigned long RandomVal (void)
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{
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int kk;
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unsigned long y;
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if (k == N) {
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for (kk = 0; kk < N - M; kk++) {
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y = (ptgfsr[kk] & UPPER_MASK) | (ptgfsr[kk + 1] & LOWER_MASK);
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ptgfsr[kk] = ptgfsr[kk + M] ^ (y >> 1) ^ mag01[y & 0x1];
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}
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for (; kk < N - 1; kk++) {
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y = (ptgfsr[kk] & UPPER_MASK) | (ptgfsr[kk + 1] & LOWER_MASK);
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ptgfsr[kk] = ptgfsr[kk + (M - N)] ^ (y >> 1) ^ mag01[y & 0x1];
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}
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y = (ptgfsr[N - 1] & UPPER_MASK) | (ptgfsr[0] & LOWER_MASK);
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ptgfsr[N - 1] = ptgfsr[M - 1] ^ (y >> 1) ^ mag01[y & 0x1];
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k = 0;
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}
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y = ptgfsr[k++];
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y ^= TEMPERING_SHIFT_U (y);
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y ^= TEMPERING_SHIFT_S (y) & TEMPERING_MASK_B;
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y ^= TEMPERING_SHIFT_T (y) & TEMPERING_MASK_C;
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return y ^= TEMPERING_SHIFT_L (y);
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}
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/*-----------------------------------------------------------------------------
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-----------------------------------------------------------------------------*/
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unsigned long RandomVal (int range)
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{
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return range ? (RandomVal () % range) : 0;
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}
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/*-----------------------------------------------------------------------------
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-----------------------------------------------------------------------------*/
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void RandomInit (unsigned long seed)
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{
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//int k;
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//memset (ptgfsr, 0, sizeof (ptgfsr));
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//mag01[0] = 0x0;
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//mag01[1] = MATRIX_A;
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ptgfsr[0] = seed;
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for (k = 1; k < N; k++)
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ptgfsr[k] = 69069 * ptgfsr[k - 1];
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k = 1;
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}
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