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-rw-r--r--libX11/src/xcms/cmsMath.c138
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diff --git a/libX11/src/xcms/cmsMath.c b/libX11/src/xcms/cmsMath.c
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+/* $Xorg: cmsMath.c,v 1.4 2001/02/09 02:03:39 xorgcvs Exp $ */
+
+/*
+
+Copyright 1990, 1998 The Open Group
+
+Permission to use, copy, modify, distribute, and sell this software and its
+documentation for any purpose is hereby granted without fee, provided that
+the above copyright notice appear in all copies and that both that
+copyright notice and this permission notice appear in supporting
+documentation.
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+Except as contained in this notice, the name of The Open Group shall not be
+used in advertising or otherwise to promote the sale, use or other dealings
+in this Software without prior written authorization from The Open Group.
+
+*/
+/* $XFree86: xc/lib/X11/cmsMath.c,v 3.4 2001/07/29 05:01:11 tsi Exp $ */
+
+/*
+ * Stephen Gildea, MIT X Consortium, January 1991
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+#include "Xlibint.h"
+#include "Xcmsint.h"
+
+#include <float.h>
+#ifndef DBL_EPSILON
+#define DBL_EPSILON 1e-6
+#endif
+
+#ifdef _X_ROOT_STATS
+int cbrt_loopcount;
+int sqrt_loopcount;
+#endif
+
+/* Newton's Method: x_n+1 = x_n - ( f(x_n) / f'(x_n) ) */
+
+
+/* for cube roots, x^3 - a = 0, x_new = x - 1/3 (x - a/x^2) */
+
+double
+_XcmsCubeRoot(double a)
+{
+ register double abs_a, cur_guess, delta;
+
+#ifdef DEBUG
+ printf("_XcmsCubeRoot passed in %g\n", a);
+#endif
+#ifdef _X_ROOT_STATS
+ cbrt_loopcount = 0;
+#endif
+ if (a == 0.)
+ return 0.;
+
+ abs_a = a<0. ? -a : a; /* convert to positive to speed loop tests */
+
+ /* arbitrary first guess */
+ if (abs_a > 1.)
+ cur_guess = abs_a/8.;
+ else
+ cur_guess = abs_a*8.;
+
+ do {
+#ifdef _X_ROOT_STATS
+ cbrt_loopcount++;
+#endif
+ delta = (cur_guess - abs_a/(cur_guess*cur_guess))/3.;
+ cur_guess -= delta;
+ if (delta < 0.) delta = -delta;
+ } while (delta >= cur_guess*DBL_EPSILON);
+
+ if (a < 0.)
+ cur_guess = -cur_guess;
+
+#ifdef DEBUG
+ printf("_XcmsCubeRoot returning %g\n", cur_guess);
+#endif
+ return cur_guess;
+}
+
+
+
+/* for square roots, x^2 - a = 0, x_new = x - 1/2 (x - a/x) */
+
+double
+_XcmsSquareRoot(double a)
+{
+ register double cur_guess, delta;
+
+#ifdef DEBUG
+ printf("_XcmsSquareRoot passed in %g\n", a);
+#endif
+#ifdef _X_ROOT_STATS
+ sqrt_loopcount = 0;
+#endif
+ if (a == 0.)
+ return 0.;
+
+ if (a < 0.) {
+ /* errno = EDOM; */
+ return 0.;
+ }
+
+ /* arbitrary first guess */
+ if (a > 1.)
+ cur_guess = a/4.;
+ else
+ cur_guess = a*4.;
+
+ do {
+#ifdef _X_ROOT_STATS
+ sqrt_loopcount++;
+#endif
+ delta = (cur_guess - a/cur_guess)/2.;
+ cur_guess -= delta;
+ if (delta < 0.) delta = -delta;
+ } while (delta >= cur_guess*DBL_EPSILON);
+
+#ifdef DEBUG
+ printf("_XcmsSquareRoot returning %g\n", cur_guess);
+#endif
+ return cur_guess;
+}
+