133 lines
2.7 KiB
C
133 lines
2.7 KiB
C
/*
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Hashing and random numbers
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <math.h>
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#include "ieee754.h"
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#include "dtypes.h"
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#include "utils.h"
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#include "hashing.h"
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#include "timefuncs.h"
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uint_t nextipow2(uint_t i)
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{
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if (i==0) return 1;
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if ((i&(i-1))==0) return i;
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if (i&TOP_BIT) return TOP_BIT;
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// repeatedly clear bottom bit
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while (i&(i-1))
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i = i&(i-1);
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return i<<1;
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}
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u_int32_t int32hash(u_int32_t a)
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{
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a = (a+0x7ed55d16) + (a<<12);
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a = (a^0xc761c23c) ^ (a>>19);
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a = (a+0x165667b1) + (a<<5);
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a = (a+0xd3a2646c) ^ (a<<9);
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a = (a+0xfd7046c5) + (a<<3);
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a = (a^0xb55a4f09) ^ (a>>16);
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return a;
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}
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u_int64_t int64hash(u_int64_t key)
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{
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key = (~key) + (key << 21); // key = (key << 21) - key - 1;
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key = key ^ (key >> 24);
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key = (key + (key << 3)) + (key << 8); // key * 265
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key = key ^ (key >> 14);
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key = (key + (key << 2)) + (key << 4); // key * 21
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key = key ^ (key >> 28);
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key = key + (key << 31);
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return key;
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}
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u_int32_t int64to32hash(u_int64_t key)
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{
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key = (~key) + (key << 18); // key = (key << 18) - key - 1;
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key = key ^ (key >> 31);
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key = key * 21; // key = (key + (key << 2)) + (key << 4);
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key = key ^ (key >> 11);
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key = key + (key << 6);
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key = key ^ (key >> 22);
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return (u_int32_t)key;
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}
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#include "lookup3.c"
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u_int64_t memhash(char* buf, size_t n)
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{
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u_int32_t c=0xcafe8881, b=0x4d6a087c;
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hashlittle2(buf, n, &c, &b);
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return (u_int64_t)c | (((u_int64_t)b)<<32);
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}
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#include "mt19937ar.c"
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double rand_double()
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{
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union ieee754_double d;
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d.ieee.mantissa0 = random();
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d.ieee.mantissa1 = random();
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d.ieee.negative = 0;
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d.ieee.exponent = IEEE754_DOUBLE_BIAS + 0; /* 2^0 */
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return d.d - 1.0;
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}
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float rand_float()
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{
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union ieee754_float f;
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f.ieee.mantissa = random();
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f.ieee.negative = 0;
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f.ieee.exponent = IEEE754_FLOAT_BIAS + 0; /* 2^0 */
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return f.f - 1.0;
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}
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double randn()
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{
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double s, vre, vim, ure, uim;
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static double next = -42;
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if (next != -42) {
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s = next;
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next = -42;
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return s;
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}
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do {
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ure = rand_double();
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uim = rand_double();
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vre = 2*ure - 1;
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vim = 2*uim - 1;
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s = vre*vre + vim*vim;
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} while (s >= 1);
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s = sqrt(-2*log(s)/s);
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next = s * vre;
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return s * vim;
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}
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void randomize()
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{
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u_int64_t tm = i64time();
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init_by_array((unsigned long*)&tm, 2);
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}
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void llt_init()
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{
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/*
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I used this function to guess good values based on epsilon:
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tol(eps) = exp(ln(eps)*-.2334012088721472)*eps
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I derived the constant by hallucinating freely.
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*/
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dbl_tolerance(1e-12);
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flt_tolerance(5e-6);
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randomize();
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}
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