add directory gnu

gnu/glibc/glibc-1.03/sysdeps/ieee754/sqrt.c

@@ -0,0 +1,120 @@
+/*
+ * Copyright (c) 1985 Regents of the University of California.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms are permitted provided
+ * that: (1) source distributions retain this entire copyright notice and
+ * comment, and (2) distributions including binaries display the following
+ * acknowledgement:  ``This product includes software developed by the
+ * University of California, Berkeley and its contributors'' in the
+ * documentation or other materials provided with the distribution and in
+ * all advertising materials mentioning features or use of this software.
+ * Neither the name of the University nor the names of its contributors may
+ * be used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+#include <ansidecl.h>
+#include <errno.h>
+#include <math.h>
+
+/* Return the square root of X.  */
+double
+DEFUN (sqrt, (x), double x)
+{
+  double q, s, b, r, t;
+  CONST double zero = 0.0;
+  int m, n, i;
+
+  /* sqrt (NaN) is NaN; sqrt (+-0) is +-0.  */
+  if (__isnan (x) || x == zero)
+    return x;
+
+  if (x < zero)
+    return zero / zero;
+
+  /* sqrt (Inf) is Inf.  */
+  if (__isinf (x))
+    return x;
+
+  /* Scale X to [1,4).  */
+  n = __logb (x);
+  x = __scalb (x, -n);
+  m = __logb (x);
+  if (m != 0)
+    /* Subnormal number.  */
+    x = __scalb (x, -m);
+
+  m += n;
+  n = m / 2;
+
+  if ((n + n) != m)
+    {
+      x *= 2;
+      --m;
+      n = m / 2;
+    }
+
+  /* Generate sqrt (X) bit by bit (accumulating in Q).  */
+  q = 1.0;
+  s = 4.0;
+  x -= 1.0;
+  r = 1;
+  for (i = 1; i <= 51; i++)
+    {
+      t = s + 1;
+      x *= 4;
+      r /= 2;
+      if (t <= x)
+	{
+	  s = t + t + 2, x -= t;
+	  q += r;
+	}
+      else
+	s *= 2;
+    }
+
+  /* Generate the last bit and determine the final rounding.  */
+  r /= 2;
+  x *= 4;
+  if (x == zero)
+    goto end;
+  (void) (100 + r);		/* Trigger inexact flag.  */
+  if (s < x)
+    {
+      q += r;
+      x -= s;
+      s += 2;
+      s *= 2;
+      x *= 4;
+      t = (x - s) - 5;
+      b = 1.0 + 3 * r / 4;
+      if (b == 1.0)
+	goto end;		/* B == 1: Round to zero.  */
+      b = 1.0 + r / 4;
+      if (b > 1.0)
+	t = 1;			/* B > 1: Round to +Inf.  */
+      if (t >= 0)
+	q += r;
+    }				/* Else round to nearest.  */
+  else
+    {
+      s *= 2;
+      x *= 4;
+      t = (x - s) - 1;
+      b = 1.0 + 3 * r / 4;
+      if (b == 1.0)
+	goto end;
+      b = 1.0 + r / 4;
+      if (b > 1.0)
+	t = 1;
+      if (t >= 0)
+	q += r;
+    }
+
+end:
+  return __scalb (q, n);
+}