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+/*
+ * Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
+ * Copyright (C) 2008 - INRIA - Arnaud TORSET
+ *
+ * This file must be used under the terms of the CeCILL.
+ * This source file is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at
+ * http://www.cecill.info/licences/Licence_CeCILL_V2-en.txt
+ *
+ */
+
+
+/*
+ URAND, A UNIVERSAL RANDOM NUMBER GENERATOR
+ BY, MICHAEL A. MALCOLM, CLEVE B. MOLER,
+ STAN-CS-73-334, JANUARY 1973,
+ COMPUTER SCIENCE DEPARTMENT,
+ School of Humanities and Sciences, STANFORD UNIVERSITY,
+ ftp://reports.stanford.edu/pub/cstr/reports/cs/tr/73/334/CS-TR-73-334.pdf
+
+*/
+
+
+
+#include "rand.h"
+#include <stdio.h>
+
+double drands(void) {
+ int m=1;
+ const int itwo=2;
+ static int m2=0,halfm=0,ia=0, ic=0, mic=0, iy=0;
+ static double s=0.0;
+
+ if (m2==0){
+ /* if first entry, compute machine integer word length */
+ while (m>m2){
+ m2=m;
+ m=itwo*m2;
+ }
+ halfm = m2;
+
+ /* compute multiplier and increment for linear congruential method */
+ ia = 8*(int)(halfm*atan(1.0)/8.0) + 5;
+ ic = 2*(int)(halfm*(0.5-sqrt(3.0)/6.0)) + 1;
+ mic = (m2 - ic) + m2;
+
+ /* s is the scale factor for converting to floating point */
+ s = 0.5/halfm;
+ }
+
+ /* compute next random number */
+ iy = iy*ia;
+
+ /* the following statement is for computers which do not allow
+ integer overflow on addition */
+ if (iy > mic) iy = (iy - m2) - m2;
+
+ iy = iy + ic;
+
+ /* the following statement is for computers where the
+ word length for addition is greater than for multiplication */
+ if (iy/2 > m2) iy = (iy - m2) - m2;
+
+ /* the following statement is for computers where integer
+ overflow affects the sign bit */
+ if (iy < 0) iy = (iy + m2) + m2;
+ return (double)iy*s;
+}
+
+