cuda-samples/Samples/quasirandomGenerator/quasirandomGenerator_gold.cpp
2021-10-21 16:34:49 +05:30

326 lines
10 KiB
C++

/* Copyright (c) 2021, NVIDIA CORPORATION. All rights reserved.
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*
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#include <stdio.h>
#include <math.h>
#include "quasirandomGenerator_common.h"
////////////////////////////////////////////////////////////////////////////////
// Table generation functions
////////////////////////////////////////////////////////////////////////////////
// Internal 64(63)-bit table
static INT64 cjn[63][QRNG_DIMENSIONS];
static int GeneratePolynomials(int buffer[QRNG_DIMENSIONS], bool primitive) {
int i, j, n, p1, p2, l;
int e_p1, e_p2, e_b;
// generate all polynomials to buffer
for (n = 1, buffer[0] = 0x2, p2 = 0, l = 0; n < QRNG_DIMENSIONS; ++n) {
// search for the next irreducible polynomial
for (p1 = buffer[n - 1] + 1;; ++p1) {
// find degree of polynomial p1
for (e_p1 = 30; (p1 & (1 << e_p1)) == 0; --e_p1) {
}
// try to divide p1 by all polynomials in buffer
for (i = 0; i < n; ++i) {
// find the degree of buffer[i]
for (e_b = e_p1; (buffer[i] & (1 << e_b)) == 0; --e_b) {
}
// divide p2 by buffer[i] until the end
for (p2 = (buffer[i] << ((e_p2 = e_p1) - e_b)) ^ p1; p2 >= buffer[i];
p2 = (buffer[i] << (e_p2 - e_b)) ^ p2) {
for (; (p2 & (1 << e_p2)) == 0; --e_p2) {
}
} // compute new degree of p2
// division without remainder!!! p1 is not irreducible
if (p2 == 0) {
break;
}
}
// all divisions were with remainder - p1 is irreducible
if (p2 != 0) {
e_p2 = 0;
if (primitive) {
// check that p1 has only one cycle (i.e. is monic, or primitive)
j = ~(0xffffffff << (e_p1 + 1));
e_b = (1 << e_p1) | 0x1;
for (p2 = e_b, e_p2 = (1 << e_p1) - 2; e_p2 > 0; --e_p2) {
p2 <<= 1;
i = p2 & p1;
i = (i & 0x55555555) + ((i >> 1) & 0x55555555);
i = (i & 0x33333333) + ((i >> 2) & 0x33333333);
i = (i & 0x07070707) + ((i >> 4) & 0x07070707);
p2 |= (i % 255) & 1;
if ((p2 & j) == e_b) break;
}
}
// it is monic - add it to the list of polynomials
if (e_p2 == 0) {
buffer[n] = p1;
l += e_p1;
break;
}
}
}
}
return l + 1;
}
////////////////////////////////////////////////////////////////////////////////
// @misc{Bratley92:LDS,
// author = "B. Fox and P. Bratley and H. Niederreiter",
// title = "Implementation and test of low discrepancy sequences",
// text = "B. L. Fox, P. Bratley, and H. Niederreiter. Implementation and
// test of
// low discrepancy sequences. ACM Trans. Model. Comput. Simul.,
// 2(3):195--213,
// July 1992.",
// year = "1992" }
////////////////////////////////////////////////////////////////////////////////
static void GenerateCJ() {
int buffer[QRNG_DIMENSIONS];
int *polynomials;
int n, p1, l, e_p1;
// Niederreiter (in contrast to Sobol) allows to use not primitive, but just
// irreducible polynomials
l = GeneratePolynomials(buffer, false);
// convert all polynomials from buffer to polynomials table
polynomials = new int[l + 2 * QRNG_DIMENSIONS + 1];
for (n = 0, l = 0; n < QRNG_DIMENSIONS; ++n) {
// find degree of polynomial p1
for (p1 = buffer[n], e_p1 = 30; (p1 & (1 << e_p1)) == 0; --e_p1) {
}
// fill polynomials table with values for this polynomial
polynomials[l++] = 1;
for (--e_p1; e_p1 >= 0; --e_p1) {
polynomials[l++] = (p1 >> e_p1) & 1;
}
polynomials[l++] = -1;
}
polynomials[l] = -1;
// irreducible polynomial p
int *p = polynomials, e, d;
// polynomial b
int b_arr[1024], *b, m;
// v array
int v_arr[1024], *v;
// temporary polynomial, required to do multiplication of p and b
int t_arr[1024], *t;
// subsidiary variables
int i, j, u, m1, ip, it;
// cycle over monic irreducible polynomials
for (d = 0; p[0] != -1; p += e + 2) {
// allocate memory for cj array for dimension (ip + 1)
for (i = 0; i < 63; ++i) {
cjn[i][d] = 0;
}
// determine the power of irreducible polynomial
for (e = 0; p[e + 1] != -1; ++e) {
}
// polynomial b in the beginning is just '1'
(b = b_arr + 1023)[m = 0] = 1;
// v array needs only (63 + e - 2) length
v = v_arr + 1023 - (63 + e - 2);
// cycle over all coefficients
for (j = 63 - 1, u = e; j >= 0; --j, ++u) {
if (u == e) {
u = 0;
// multiply b by p (polynomials multiplication)
for (i = 0, t = t_arr + 1023 - (m1 = m); i <= m; ++i) {
t[i] = b[i];
}
b = b_arr + 1023 - (m += e);
for (i = 0; i <= m; ++i) {
b[i] = 0;
for (ip = e - (m - i), it = m1; ip <= e && it >= 0; ++ip, --it) {
if (ip >= 0) {
b[i] ^= p[ip] & t[it];
}
}
}
// multiplication of polynomials finished
// calculate v
for (i = 0; i < m1; ++i) {
v[i] = 0;
}
for (; i < m; ++i) {
v[i] = 1;
}
for (; i <= 63 + e - 2; ++i) {
v[i] = 0;
for (it = 1; it <= m; ++it) {
v[i] ^= v[i - it] & b[it];
}
}
}
// copy calculated v to cj
for (i = 0; i < 63; i++) {
cjn[i][d] |= (INT64)v[i + u] << j;
}
}
++d;
}
delete[] polynomials;
}
// Generate 63-bit quasirandom number for given index and dimension and
// normalize
extern "C" double getQuasirandomValue63(INT64 i, int dim) {
const double INT63_SCALE = (1.0 / (double)0x8000000000000001ULL);
INT64 result = 0;
for (int bit = 0; bit < 63; bit++, i >>= 1)
if (i & 1) result ^= cjn[bit][dim];
return (double)(result + 1) * INT63_SCALE;
}
////////////////////////////////////////////////////////////////////////////////
// Initialization (table setup)
////////////////////////////////////////////////////////////////////////////////
extern "C" void initQuasirandomGenerator(
unsigned int table[QRNG_DIMENSIONS][QRNG_RESOLUTION]) {
GenerateCJ();
for (int dim = 0; dim < QRNG_DIMENSIONS; dim++)
for (int bit = 0; bit < QRNG_RESOLUTION; bit++)
table[dim][bit] = (int)((cjn[bit][dim] >> 32) & 0x7FFFFFFF);
}
////////////////////////////////////////////////////////////////////////////////
// Generate 31-bit quasirandom number for given index and dimension
////////////////////////////////////////////////////////////////////////////////
extern "C" float getQuasirandomValue(
unsigned int table[QRNG_DIMENSIONS][QRNG_RESOLUTION], int i, int dim) {
int result = 0;
for (int bit = 0; bit < QRNG_RESOLUTION; bit++, i >>= 1)
if (i & 1) result ^= table[dim][bit];
return (float)(result + 1) * INT_SCALE;
}
////////////////////////////////////////////////////////////////////////////////
// Moro's Inverse Cumulative Normal Distribution function approximation
////////////////////////////////////////////////////////////////////////////////
extern "C" double MoroInvCNDcpu(unsigned int x) {
const double a1 = 2.50662823884;
const double a2 = -18.61500062529;
const double a3 = 41.39119773534;
const double a4 = -25.44106049637;
const double b1 = -8.4735109309;
const double b2 = 23.08336743743;
const double b3 = -21.06224101826;
const double b4 = 3.13082909833;
const double c1 = 0.337475482272615;
const double c2 = 0.976169019091719;
const double c3 = 0.160797971491821;
const double c4 = 2.76438810333863E-02;
const double c5 = 3.8405729373609E-03;
const double c6 = 3.951896511919E-04;
const double c7 = 3.21767881768E-05;
const double c8 = 2.888167364E-07;
const double c9 = 3.960315187E-07;
double z;
bool negate = false;
// Ensure the conversion to floating point will give a value in the
// range (0,0.5] by restricting the input to the bottom half of the
// input domain. We will later reflect the result if the input was
// originally in the top half of the input domain
if (x >= 0x80000000UL) {
x = 0xffffffffUL - x;
negate = true;
}
// x is now in the range [0,0x80000000) (i.e. [0,0x7fffffff])
// Convert to floating point in (0,0.5]
const double x1 = 1.0 / static_cast<double>(0xffffffffUL);
const double x2 = x1 / 2.0;
double p1 = x * x1 + x2;
// Convert to floating point in (-0.5,0]
double p2 = p1 - 0.5;
// The input to the Moro inversion is p2 which is in the range
// (-0.5,0]. This means that our output will be the negative side
// of the bell curve (which we will reflect if "negate" is true).
// Main body of the bell curve for |p| < 0.42
if (p2 > -0.42) {
z = p2 * p2;
z = p2 * (((a4 * z + a3) * z + a2) * z + a1) /
((((b4 * z + b3) * z + b2) * z + b1) * z + 1.0);
}
// Special case (Chebychev) for tail
else {
z = log(-log(p1));
z = -(c1 + z * (c2 + z * (c3 + z * (c4 + z * (c5 + z * (c6 + z *
(c7 + z * (c8 + z * c9))))))));
}
// If the original input (x) was in the top half of the range, reflect
// to get the positive side of the bell curve
return negate ? -z : z;
}