Created
November 19, 2015 22:04
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Pi
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#include <iostream> | |
#include <cmath> | |
#include <omp.h> | |
#include <gmp.h> | |
#define LOG2_10 3.321928094887362 | |
std::string pi(size_t places) { | |
size_t scaled = ceil(static_cast<double>(places) / 14); | |
mpf_set_default_prec(LOG2_10 * places); | |
mpf_t fpi; mpf_init(fpi); | |
omp_lock_t write_lock; | |
omp_init_lock(&write_lock); | |
#pragma omp parallel | |
{ | |
mpz_t ztmp, den; | |
mpz_inits(ztmp, den, nullptr); | |
mpf_t ftmp[2]; | |
mpf_t partial; mpf_init_set_ui(partial, 0); | |
mpf_inits(ftmp[0], ftmp[1], nullptr); | |
#pragma omp for | |
for (size_t k = 0; k < scaled; k++) { | |
mpz_fac_ui(ztmp, 6 * k); | |
mpf_set_z(*ftmp, ztmp); | |
mpf_mul_ui(*ftmp, *ftmp, 545140134 * k + 13591409); | |
mpz_fac_ui(den, k); | |
mpz_pow_ui(den, den, 3); | |
mpz_fac_ui(ztmp, 3 * k); | |
mpz_mul(den, den, ztmp); | |
mpz_ui_pow_ui(ztmp, 640320, 3 * k); | |
if (k & 1) mpz_neg(ztmp, ztmp); | |
mpz_mul(den, den, ztmp); | |
mpf_set_z(ftmp[1], den); | |
mpf_div(ftmp[0], ftmp[0], ftmp[1]); | |
mpf_add(partial, partial, ftmp[0]); | |
} | |
omp_set_lock(&write_lock); | |
mpf_add(fpi, fpi, partial); | |
omp_unset_lock(&write_lock); | |
mpf_clear(partial); | |
mpf_clears(ftmp[0], ftmp[1], nullptr); | |
mpz_clears(ztmp, den, nullptr); | |
} | |
omp_destroy_lock(&write_lock); | |
mpz_t ztmp, den; | |
mpz_inits(ztmp, den, nullptr); | |
mpf_t ftmp[2]; | |
mpf_inits(ftmp[0], ftmp[1], nullptr); | |
mpf_set_ui(*ftmp, 426880); | |
mpf_div(fpi, *ftmp, fpi); | |
mpf_sqrt_ui(*ftmp, 10005); | |
mpf_mul(fpi, fpi, *ftmp); | |
char buf[places + 3]; | |
int off = gmp_snprintf(buf, places + 2, "%.*Ff\n", places, fpi); | |
buf[off] = '\0'; | |
mpf_clears(ftmp[0], ftmp[1], fpi, nullptr); | |
mpz_clears(ztmp, den, nullptr); | |
return buf; | |
} | |
int main() { | |
auto pi_str = pi(50000); | |
// auto pi_str = pi(10000); | |
std::cout << pi_str << std::endl; | |
} |
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