complex_t *polynomial_eval(polynomial_t *p, complex_t *coef, monomial_t *m, complex_t *eval)
{
complex_t *result = NULL, *tmp = NULL;
unsigned long diff = 0;
if (p == NULL || coef == NULL || eval == NULL)
return NULL;
if (p->first->degree == 0)
return complex_init(coef->re, coef->im);
else
{
diff = (m == NULL) ? p->last->degree : m->previous->degree - m->degree;
while (diff > 0)
{
if (result == NULL)
{
result = complex_prod(coef, eval);
if (result == NULL)
return NULL;
}
else
{
tmp = complex_prod(result, eval);
if (tmp == NULL)
{
complex_free(result);
return NULL;
}
complex_free(result);
result = tmp;
}
diff--;
}
if (m != NULL)
{
tmp = complex_sum(result, m->coef);
if (tmp == NULL)
{
complex_free(result);
return NULL;
}
complex_free(result);
result = tmp;
if (m->next != NULL || m->degree > 0)
{
result = polynomial_eval(p, tmp, m->next, eval);
complex_free(tmp);
}
}
return result;
}
}
double
log_gamma(double x)
{
double p, q, u, w, z;
int i;
int sgngam = 1;
if (x >= MY_kDBL_MAX)
return(MY_kDBL_MAX);
if( x < -34.0 )
{
q = -x;
w = log_gamma(q);
p = floor(q);
if( p==q )//_unur_FP_same(p,q)
return(MY_kDBL_MAX);
i = (int) p;
if( (i & 1) == 0 )
sgngam = -1;
else
sgngam = 1;
z = q - p;
if( z > 0.5 )
{
p += 1.0;
z = p - q;
}
z = q * sin( M_PI * z );
if( z == 0 )
return(MY_kDBL_MAX);
z = log(M_PI) - log( z ) - w;
return( z );
}
if( x < 13.0 )
{
z = 1.0;
p = 0.0;
u = x;
while( u >= 3.0 )
{
p -= 1.0;
u = x + p;
z *= u;
}
while( u < 2.0 )
{
if( u == 0 )
return (MY_kDBL_MAX);
z /= u;
p += 1.0;
u = x + p;
}
if( z < 0.0 )
{
sgngam = -1;
z = -z;
}
else
sgngam = 1;
if( u == 2.0 )
return( log(z) );
p -= 2.0;
x = x + p;
p = x * polynomial_eval(x, B, 5 ) / polynomial_1eval( x, C, 6);
return( log(z) + p );
}
if( x > MY_kMAXLGM )
return( sgngam * MY_kDBL_MAX );
q = ( x - 0.5 ) * log(x) - x + MY_kLS2PI;
if( x > 1.0e8 )
return( q );
p = 1.0/(x*x);
if( x >= 1000.0 )
q += (( 7.9365079365079365079365e-4 * p
- 2.7777777777777777777778e-3) *p
+ 0.0833333333333333333333) / x;
else
q += polynomial_eval( p, A, 4 ) / x;
return( q );
}
