* device/lib/pic/libm: NEW, added math library functions

[fw/sdcc] / device / lib / pic / libm / sqrtf.c

diff --git a/device/lib/pic/libm/sqrtf.c b/device/lib/pic/libm/sqrtf.c
new file mode 100644 (file)
index 0000000..a35e600
--- /dev/null
+++ b/device/lib/pic/libm/sqrtf.c
@@ -0,0 +1,56 @@
+/*  sqrtf.c:  Computes square root of a 32-bit float as outlined in [1]
+
+    Copyright (C) 2001, 2002  Jesus Calvino-Fraga, jesusc@ieee.org 
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Lesser General Public
+    License as published by the Free Software Foundation; either
+    version 2.1 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public
+    License along with this library; if not, write to the Free Software
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA */
+
+/* [1] William James Cody and W.  M.  Waite.  _Software manual for the
+   elementary functions_, Englewood Cliffs, N.J.:Prentice-Hall, 1980. */
+
+/* Version 1.0 - Initial release */
+
+/*
+** $Id: sqrtf.c 3654 2005-01-24 10:38:53Z vrokas $
+*/
+
+#include <float.h>
+#include <math.h>
+#include <errno.h>
+
+float sqrtf(const float x) _MATH_REENTRANT
+{
+    float f, y;
+    FS_STATIC int n;
+
+    if (x==0.0) return x;
+    else if (x==1.0) return 1.0;
+    else if (x<0.0)
+    {
+        errno=EDOM;
+        return 0.0;
+    }
+    f=frexpf(x, &n);
+    y=0.41731+0.59016*f; /*Educated guess*/
+    /*For a 24 bit mantisa (float), two iterations are sufficient*/
+    y+=f/y;
+    y=ldexpf(y, -2) + f/y; /*Faster version of 0.25 * y + f/y*/
+
+    if (n&1)
+    {
+        y*=0.7071067812;
+        ++n;
+    }
+    return ldexpf(y, n/2);
+}