/*
compute int *n = round_to_nearest_int(a / log(2))
M_APM b = MAPM version of *n
returns 0: OK
-1, 1: failure
*/
int M_exp_compute_nn(int *n, M_APM b, M_APM a)
{
M_APM tmp0, tmp1;
void *vp;
char *cp, sbuf[48];
int kk;
*n = 0;
vp = NULL;
cp = sbuf;
tmp0 = M_get_stack_var();
tmp1 = M_get_stack_var();
/* find 'n' and convert it to a normal C int */
/* we just need an approx 1/log(2) for this calculation */
m_apm_multiply(tmp1, a, MM_exp_log2R);
/* round to the nearest int */
if (tmp1->m_apm_sign >= 0)
{
m_apm_add(tmp0, tmp1, MM_0_5);
m_apm_floor(tmp1, tmp0);
}
else
{
m_apm_subtract(tmp0, tmp1, MM_0_5);
m_apm_ceil(tmp1, tmp0);
}
kk = tmp1->m_apm_exponent;
if (kk >= 42)
{
if ((vp = (void *)MAPM_MALLOC((kk + 16) * sizeof(char))) == NULL)
{
/* fatal, this does not return */
M_apm_log_error_msg(M_APM_FATAL, "\'M_exp_compute_nn\', Out of memory");
}
cp = (char *)vp;
}
m_apm_to_integer_string(cp, tmp1);
*n = atoi(cp);
m_apm_set_long(b, (long)(*n));
kk = m_apm_compare(b, tmp1);
if (vp != NULL)
MAPM_FREE(vp);
M_restore_stack(2);
return(kk);
}
void m_apm_floor_mt(M_APM bb, M_APM aa)
{
m_apm_enter();
m_apm_floor(bb,aa);
m_apm_leave();
}
