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| 1 | /* | |
| 2 | * Lightweight adaptation of the example multiply with carry PRNG | |
| 3 | * code from wikipedia | |
| 4 | - | * Version: 1 |
| 4 | + | * Version: 2 |
| 5 | */ | |
| 6 | ||
| 7 | #include <stdint.h> | |
| 8 | ||
| 9 | - | #define PHI 0x9e3779b9 |
| 9 | + | #define MWC_A 18782LL |
| 10 | #define MWC_R 0xfffffffe | |
| 11 | ||
| 12 | static uint32_t Q, c = 362436; | |
| 13 | ||
| 14 | void init_rand(uint32_t x) | |
| 15 | { Q = x;
| |
| 16 | } | |
| 17 | ||
| 18 | - | { uint64_t t, a = 18782LL;
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| 18 | + | |
| 19 | - | uint32_t x, r = 0xfffffffe; |
| 19 | + | { uint32_t x;
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| 20 | - | t = a * Q + c; |
| 20 | + | uint64_t t = MWC_A * Q + c; |
| 21 | c = (t >> 32); | |
| 22 | x = t + c; | |
| 23 | if(x < c) | |
| 24 | { x++;
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| 25 | c++; | |
| 26 | } | |
| 27 | - | return (Q = r - x); |
| 27 | + | return (Q = MWC_R - x); |
| 28 | } |
