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/*
* http://www.cut-the-knot.org/Curriculum/Algorithms/SpigotForPi.shtml
*
* Original code is available in public domain
* Pi Decimal Point Calculation using BBP (named after Bailey-Borwein-Plouffe)
*
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <wchar.h>
#include <time.h>
#include <sys/time.h>
/* globals */
int printed = 0;
int line = 1;
int mulof2 = 1;
/* function prototypes */
inline void out_dig(long unsigned, struct timeval *);
inline void printTime(struct timeval *);
int do_calc(char **);
inline void out_dig(long unsigned dig, struct timeval *before)
{
putchar(dig);
printed++;
if ((printed % 50) == 0)
{
if ((line % (20 * mulof2)) == 0)
{
printf("\n%dK: ", mulof2);
mulof2 *= 2;
printTime(before);
}
printf("\nd %06d: ", 50 * line);
line++;
}
else if ((printed % 10) == 0)
putchar(' ');
}
inline void printTime(struct timeval *before)
{
struct timeval after;
gettimeofday(&after, 0);
long unsigned int elapsed_ms = (after.tv_sec - before->tv_sec) * 1000 +
(after.tv_usec - before->tv_usec) / 1000;
unsigned int seconds_n = elapsed_ms / 1000;
unsigned int milliseconds_n = elapsed_ms % 1000;
printf("time elapsed: %u.%u seconds\n", seconds_n, milliseconds_n);
}
int do_calc(char **argv)
{
long unsigned int i, j, nines, predigit;
long unsigned int q, x, digits_n, len;
long unsigned int *pi;
long unsigned int alloc;
digits_n = atol(argv[1]);
if (digits_n < 1)
return -1;
len = (digits_n * 10) / 3;
alloc = sizeof(long unsigned int) * (len+1);
pi = (long unsigned int *) malloc(alloc);
if (!pi)
{
perror("malloc");
exit(-1);
}
else
printf("\n\tPi Decimal Digit Calculation\n"
"allocated %ldKb of heap memory\n", alloc / 1024);
for (i = 0; i < len; i++)
pi[i] = 2;
/* wchar_t pi_c = 0x03c0; */
printf("Pi value: 3.");
nines = 0;
predigit = 0;
struct timeval before;
gettimeofday(&before, 0);
for (j = 0; j <= digits_n; j++)
{
q = 0;
for (i = len; i > 0; i--)
{
x = 10 * pi[i] + q * i;
pi[i] = x % (2 * i - 1);
q = x / (2 * i - 1);
}
pi[1] = q % 10;
q = q / 10;
if (q == 9)
nines++;
else if (q == 10)
{
out_dig('1' + predigit, &before);
while (nines)
{
out_dig('0', &before);
nines--;
}
predigit = 0;
fflush(stdout);
}
else
{
if (j > 1)
out_dig('0' + predigit, &before);
while (nines)
{
out_dig('9', &before);
nines--;
}
predigit = q;
fflush(stdout);
}
}
out_dig(predigit + '0', &before);
puts("");
free(pi);
struct timeval after;
gettimeofday(&after, 0);
long unsigned int elapsed_ms = (after.tv_sec - before.tv_sec) * 1000 +
(after.tv_usec - before.tv_usec) / 1000;
unsigned int seconds_n = elapsed_ms / 1000;
unsigned int milliseconds_n = elapsed_ms % 1000;
printf("\nPi calculation to %lu'th decimal point finished\n"
"\tTotal Time: %u.%u seconds\n", digits_n, seconds_n, milliseconds_n);
return 1;
}
int main(int argc, char *argv[])
{
if (argc < 2)
{
fprintf(stderr, "%s <number of decimal digits to compute>\n", argv[0]);
return 1;
}
if (!do_calc(argv))
printf("do_calc() failed to execute\n");
return 0;
}
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