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https://github.com/naehrwert/scetool.git
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50 lines
1.1 KiB
C++
50 lines
1.1 KiB
C++
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#include "mt19937.h"
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void mt19937_init(mt19937_ctxt_t *ctxt, unsigned int seed)
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{
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ctxt->state[0] = seed;
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for(ctxt->idx = 1; ctxt->idx < MT_N; ctxt->idx++)
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ctxt->state[ctxt->idx] = (1812433253 * (ctxt->state[ctxt->idx - 1] ^ (ctxt->state[ctxt->idx - 1] >> 30)) + ctxt->idx);
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ctxt->idx = MT_M + 1;
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}
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unsigned int mt19937_update(mt19937_ctxt_t *ctxt)
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{
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unsigned int y, k;
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static unsigned int mag01[2] = {0, MT_MATRIX_A};
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if(ctxt->idx >= MT_N)
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{
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for(k = 0; k < MT_N - MT_M; k++)
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{
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y = (ctxt->state[k] & MT_UPPER_MASK) |
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(ctxt->state[k + 1] & MT_LOWER_MASK);
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ctxt->state[k] = ctxt->state[k + MT_M] ^ (y >> 1) ^ mag01[y & 1];
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}
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for(; k < MT_N - 1; k++)
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{
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y = (ctxt->state[k] & MT_UPPER_MASK) |
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(ctxt->state[k + 1] & MT_LOWER_MASK);
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ctxt->state[k] = ctxt->state[k + (MT_M - MT_N)] ^ (y >> 1) ^ mag01[y & 1];
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}
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y = (ctxt->state[MT_N - 1] & MT_UPPER_MASK) |
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(ctxt->state[0] & MT_LOWER_MASK);
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ctxt->state[MT_N - 1] = ctxt->state[MT_M - 1] ^ (y >> 1) ^ mag01[y & 1];
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ctxt->idx = 0;
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}
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y = ctxt->state[ctxt->idx++];
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y ^= (y >> 11);
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y ^= (y << 7) & 0x9d2c5680UL;
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y ^= (y << 15) & 0xefc60000UL;
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y ^= (y >> 18);
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return y;
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}
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