random generator functions

src/maths/misc/randnumb.c

@@ -0,0 +1,79 @@
+/**********
+Copyright 2008 Holger Vogt
+**********/
+/* Care about random numbers
+   The seed value is set as random number in main.c, line 746.
+   A fixed seed value may be set by 'set rndseed=value'.
+*/
+
+#include "ngspice.h"
+#include "cpdefs.h"
+#include "ftedefs.h"
+#include "../frontend/variable.h"
+
+
+/* MINGW: random, srandom in libiberty.a, but not in libiberty.h */
+#if defined(__MINGW32__) && defined(HAVE_RANDOM)
+extern long int random (void);
+extern void srandom (unsigned int seed);
+#endif
+
+void checkseed(void);
+double drand(void);
+double gauss(void);
+
+
+/* Check if a seed has been set by the command 'set rndseed=value'
+   in spinit with integer value > 0. If available, call srand(value).
+   This will override the call to srand in main.c.
+   Checkseed should be put in front of any call to random or rand.
+*/
+void checkseed()
+{
+   int newseed;
+   static int oldseed;
+/*   printf("Enter checkseed()\n"); */
+   if (cp_getvar("rndseed", VT_NUM, &newseed)) {
+      if ((newseed > 0) && (oldseed != newseed)) {
+         srandom(newseed);
+         oldseed = newseed;
+         printf("Seed value for random number generator is set to %d\n", newseed);
+      }
+/*      else printf("Oldseed %d, newseed %d\n", oldseed, newseed); */
+   }
+   
+}
+
+/* uniform random number generator, interval -1 .. +1 */
+double drand()
+{
+   checkseed();
+   return ( 2.0*((double) (RR_MAX-abs(random())) / (double)RR_MAX-0.5));
+}
+
+
+/***  gauss  ***/
+
+double gauss()
+{
+  static bool gliset = TRUE;
+  static double glgset = 0.0;
+  double fac,r,v1,v2;
+  if (gliset) {
+    do {
+      v1 = drand();  v2 = drand();
+      r = v1*v1 + v2*v2;
+    } while (r >= 1.0);
+/*    printf("v1 %f, v2 %f\n", v1, v2); */
+    fac = sqrt(-2.0 * log(r) / r);
+    glgset = v1 * fac;
+    gliset = FALSE;
+    return v2 * fac;
+  } else {
+    gliset = TRUE;
+    return glgset;
+  }
+}
+
+
+