double hyperg(double a, double b, double x)
{
double asum, psum, acanc, pcanc = 0, temp;
/* See if a Kummer transformation will help */
temp = b - a;
if (fabs(temp) < 0.001 * fabs(a))
return(exp(x) * hyperg(temp, b, -x));
psum = hy1f1p(a, b, x, &pcanc);
if (pcanc < 1.0e-15)
goto done;
/* try asymptotic series */
asum = hy1f1a(a, b, x, &acanc);
/* Pick the result with less estimated error */
if (acanc < pcanc) {
pcanc = acanc;
psum = asum;
}
done:
if (pcanc > 1.0e-12) {
it_warning("hyperg(): partial loss of precision");
}
return(psum);
}
double hyperg (double a, double b, double x)
{
double asum, psum, acanc, temp, pcanc = 0;
/* See if a Kummer transformation will help */
temp = b - a;
if (fabs(temp) < 0.001 * fabs(a))
return exp(x) * hyperg(temp, b, -x);
psum = hy1f1p(a, b, x, &pcanc);
if (pcanc < 1.0e-15)
goto done;
/* try asymptotic series */
asum = hy1f1a(a, b, x, &acanc);
/* Pick the result with less estimated error */
if (acanc < pcanc) {
pcanc = acanc;
psum = asum;
}
done:
if (pcanc > 1.0e-12)
mtherr("hyperg", CEPHES_PLOSS);
return psum;
}