mirror of
https://github.com/autc04/Retro68.git
synced 2024-08-28 03:29:05 +00:00
58 lines
1004 B
C
58 lines
1004 B
C
#include "quadmath-imp.h"
|
|
#include <math.h>
|
|
#include <float.h>
|
|
|
|
__float128
|
|
sqrtq (const __float128 x)
|
|
{
|
|
__float128 y;
|
|
int exp;
|
|
|
|
if (x == 0)
|
|
return x;
|
|
|
|
if (isnanq (x))
|
|
return x;
|
|
|
|
if (x < 0)
|
|
return nanq ("");
|
|
|
|
if (x <= DBL_MAX && x >= DBL_MIN)
|
|
{
|
|
/* Use double result as starting point. */
|
|
y = sqrt ((double) x);
|
|
|
|
/* Two Newton iterations. */
|
|
y -= 0.5q * (y - x / y);
|
|
y -= 0.5q * (y - x / y);
|
|
return y;
|
|
}
|
|
|
|
#ifdef HAVE_SQRTL
|
|
if (x <= LDBL_MAX && x >= LDBL_MIN)
|
|
{
|
|
/* Use long double result as starting point. */
|
|
y = sqrtl ((long double) x);
|
|
|
|
/* One Newton iteration. */
|
|
y -= 0.5q * (y - x / y);
|
|
return y;
|
|
}
|
|
#endif
|
|
|
|
/* If we're outside of the range of C types, we have to compute
|
|
the initial guess the hard way. */
|
|
y = frexpq (x, &exp);
|
|
if (exp % 2)
|
|
y *= 2, exp--;
|
|
|
|
y = sqrt (y);
|
|
y = scalbnq (y, exp / 2);
|
|
|
|
/* Two Newton iterations. */
|
|
y -= 0.5q * (y - x / y);
|
|
y -= 0.5q * (y - x / y);
|
|
return y;
|
|
}
|
|
|