1 /* sqrtf.c: Computes square root of a 32-bit float as outlined in [1]
3 Copyright (C) 2001, 2002 Jesus Calvino-Fraga, jesusc@ieee.org
5 This library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 This library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with this library; if not, write to the Free Software
17 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
19 /* [1] William James Cody and W. M. Waite. _Software manual for the
20 elementary functions_, Englewood Cliffs, N.J.:Prentice-Hall, 1980. */
22 /* Version 1.0 - Initial release */
27 float sqrtf(const float x) reentrant
33 else if (x==1.0) return 1.0;
40 y=0.41731+0.59016*f; /*Educated guess*/
41 /*For a 24 bit mantisa (float), two iterations are sufficient*/
43 y=ldexpf(y, -2) + f/y; /*Faster version of 0.25 * y + f/y*/
50 return ldexpf(y, n/2);