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Subjectpi.c
 Hi all!

I am not really sure, if this mail is offtopic - sorry,
but to this list contribute most linux gurus.

I have following problem: When I compile this program
(taken from snip9510.zip)
------- pi.c -------

/*
** PI.C - Computes Pi to an arbitrary number of digits
**
** Uses far arrays so may be compiled in any memory model
*/

#include <stdio.h>
#include <stdlib.h>

long kf, ks;
long *mf, *ms;
long cnt, n, temp, nd;
long i;
long col, col1;
long loc, stor[21];

void shift(long *l1, long *l2, long lp, long lmod)
{
long k;

k = ((*l2) > 0 ? (*l2) / lmod: -(-(*l2) / lmod) - 1);
*l2 -= k * lmod;
*l1 += k * lp;
}

void yprint(long m)
{
if (cnt<n)
{
if (++col == 11)
{
col = 1;
if (++col1 == 6)
{
col1 = 0;
printf("\n");
printf("%4ld",m%10);
}
else printf("%3ld",m%10);
}
else printf("%ld",m);
cnt++;
}
}

void xprint(long m)
{
long ii, wk, wk1;

if (m < 8)
{
for (ii = 1; ii <= loc; )
yprint(stor[(int)(ii++)]);
loc = 0;
}
else
{
if (m > 9)
{
wk = m / 10;
m %= 10;
for (wk1 = loc; wk1 >= 1; wk1--)
{
wk += stor[(int)wk1];
stor[(int)wk1] = wk % 10;
wk /= 10;
}
}
}
stor[(int)(++loc)] = m;
}

void memerr(int errno)
{
printf("\a\nOut of memory error #%d\n", errno);
if (2 == errno)
free(mf);
_exit(2);
}

int main(int argc, char *argv[])
{
int i=0;
char *endp;

stor[i++] = 0;
if (argc < 2)
{
puts("\aUsage: PI <number_of_digits>");
return(1);
}
n = strtol(argv[1], &endp, 10);
mf = malloc((size_t)(n + 3L)*(size_t)sizeof(long));
if (!mf)
memerr(1);
ms = malloc((size_t)(n + 3L)*(size_t)sizeof(long));
if (!ms)
memerr(2);
printf("\nApproximation of PI to %ld digits\n", (long)n);
cnt = 0;
kf = 25;
ks = 57121L;
mf[1] = 1L;
for (i = 2; i <= (int)n; i += 2)
{
mf[i] = -16L;
mf[i+1] = 16L;
}
for (i = 1; i <= (int)n; i += 2)
{
ms[i] = -4L;
ms[i+1] = 4L;
}
printf("\n 3.");
while (cnt < n)
{
for (i = 0; ++i <= (int)n - (int)cnt; )
{
mf[i] *= 10L;
ms[i] *= 10L;
}
for (i =(int)(n - cnt + 1); --i >= 2; )
{
temp = 2 * i - 1;
shift(&mf[i - 1], &mf[i], temp - 2, temp * kf);
shift(&ms[i - 1], &ms[i], temp - 2, temp * ks);
}
nd = 0;
shift((long *)&nd, &mf[1], 1L, 5L);
shift((long *)&nd, &ms[1], 1L, 239L);
xprint(nd);
}
printf("\n\nCalculations Completed!\n");
free(ms);
free(mf);
return(0);
}
------- -------
in ELF format, it runs ok up to 3247 digits.
Approximation to 3248 digits gives core dumping.
Compilled as a.out work properly.
(tested on SLACKWARE 3.1 ELF and RH3.0.3)

Can somebody explain it to me?

Thanks in advance!

Filip Zaludek, filip@cti.cz


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