From 1077fa4d772832f77a677ce7fb7c2d513b959e3f Mon Sep 17 00:00:00 2001
From: Eric Andersen <andersen@codepoet.org>
Date: Thu, 10 May 2001 00:40:28 +0000
Subject: uClibc now has a math library.  muahahahaha!  -Erik

---
 libm/float/sqrtf.c | 140 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+)
 create mode 100644 libm/float/sqrtf.c

(limited to 'libm/float/sqrtf.c')

diff --git a/libm/float/sqrtf.c b/libm/float/sqrtf.c
new file mode 100644
index 000000000..bc75a907b
--- /dev/null
+++ b/libm/float/sqrtf.c
@@ -0,0 +1,140 @@
+/*							sqrtf.c
+ *
+ *	Square root
+ *
+ *
+ *
+ * SYNOPSIS:
+ *
+ * float x, y, sqrtf();
+ *
+ * y = sqrtf( x );
+ *
+ *
+ *
+ * DESCRIPTION:
+ *
+ * Returns the square root of x.
+ *
+ * Range reduction involves isolating the power of two of the
+ * argument and using a polynomial approximation to obtain
+ * a rough value for the square root.  Then Heron's iteration
+ * is used three times to converge to an accurate value.
+ *
+ *
+ *
+ * ACCURACY:
+ *
+ *
+ *                      Relative error:
+ * arithmetic   domain     # trials      peak         rms
+ *    IEEE      0,1.e38     100000       8.7e-8     2.9e-8
+ *
+ *
+ * ERROR MESSAGES:
+ *
+ *   message         condition      value returned
+ * sqrtf domain        x < 0            0.0
+ *
+ */
+
+/*
+Cephes Math Library Release 2.2:  June, 1992
+Copyright 1984, 1987, 1988, 1992 by Stephen L. Moshier
+Direct inquiries to 30 Frost Street, Cambridge, MA 02140
+*/
+
+/* Single precision square root
+ * test interval: [sqrt(2)/2, sqrt(2)]
+ * trials: 30000
+ * peak relative error: 8.8e-8
+ * rms relative error: 3.3e-8
+ *
+ * test interval: [0.01, 100.0]
+ * trials: 50000
+ * peak relative error: 8.7e-8
+ * rms relative error: 3.3e-8
+ *
+ * Copyright (C) 1989 by Stephen L. Moshier.  All rights reserved.
+ */
+#include <math.h>
+
+#ifdef ANSIC
+float frexpf( float, int * );
+float ldexpf( float, int );
+
+float sqrtf( float xx )
+#else
+float frexpf(), ldexpf();
+
+float sqrtf(xx)
+float xx;
+#endif
+{
+float f, x, y;
+int e;
+
+f = xx;
+if( f <= 0.0 )
+	{
+	if( f < 0.0 )
+		mtherr( "sqrtf", DOMAIN );
+	return( 0.0 );
+	}
+
+x = frexpf( f, &e );	/* f = x * 2**e,   0.5 <= x < 1.0 */
+/* If power of 2 is odd, double x and decrement the power of 2. */
+if( e & 1 )
+	{
+	x = x + x;
+	e -= 1;
+	}
+
+e >>= 1;	/* The power of 2 of the square root. */
+
+if( x > 1.41421356237 )
+	{
+/* x is between sqrt(2) and 2. */
+	x = x - 2.0;
+	y =
+	((((( -9.8843065718E-4 * x
+	  + 7.9479950957E-4) * x
+	  - 3.5890535377E-3) * x
+	  + 1.1028809744E-2) * x
+	  - 4.4195203560E-2) * x
+	  + 3.5355338194E-1) * x
+	  + 1.41421356237E0;
+	goto sqdon;
+	}
+
+if( x > 0.707106781187 )
+	{
+/* x is between sqrt(2)/2 and sqrt(2). */
+	x = x - 1.0;
+	y =
+	((((( 1.35199291026E-2 * x
+	  - 2.26657767832E-2) * x
+	  + 2.78720776889E-2) * x
+	  - 3.89582788321E-2) * x
+	  + 6.24811144548E-2) * x
+	  - 1.25001503933E-1) * x * x
+	  + 0.5 * x
+	  + 1.0;
+	goto sqdon;
+	}
+
+/* x is between 0.5 and sqrt(2)/2. */
+x = x - 0.5;
+y =
+((((( -3.9495006054E-1 * x
+  + 5.1743034569E-1) * x
+  - 4.3214437330E-1) * x
+  + 3.5310730460E-1) * x
+  - 3.5354581892E-1) * x
+  + 7.0710676017E-1) * x
+  + 7.07106781187E-1;
+
+sqdon:
+y = ldexpf( y, e );  /* y = y * 2**e */
+return( y);
+}
-- 
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