redo random number generation

wallace.c, main.c, randnumb.c, sharedspice.c:
set a seed value by getpid, may be overridden by 'set rndseed=val'
add func gauss1() returning only a single value
speed up gauss0()
add checkseed() to rgauss() and poisson() to read 'rndseed', if changed

src/frontend/trannoise/wallace.c

@@ -79,10 +79,12 @@ initw(void)
     double totsqr, nomsqr;
     unsigned int coa;
 
+#ifdef HasMain
     /* initialize the uniform generator */
     srand((unsigned int) getpid());
     // srand(17);
     TausSeed();
+#endif
 
     ScaleGauss = 1.;
     newpools = 1;

src/include/ngspice/randnumb.h

@@ -7,6 +7,7 @@ extern void initw(void);
 extern void checkseed(void);    /* seed random or set by 'set rndseed=value'*/
 extern double drand(void);
 extern double gauss0(void);
+extern double gauss1(void);
 extern int poisson(double);
 extern double exprand(double);
 

src/main.c

@@ -887,8 +887,9 @@ main(int argc, char **argv)
 
     cp_program = ft_sim->simulator;
 
-    srand((unsigned int) getpid());
-    TausSeed();
+    int ii = getpid();
+    cp_vset("rndseed", CP_NUM, &ii);
+    checkseed();
 
     /* --- Process command line options --- */
     for (;;) {
@@ -1188,15 +1189,7 @@ main(int argc, char **argv)
             fprintf(cp_out, "SoS %f, seed value: %ld\n", renormalize(), rseed);
         }
 #elif defined(WaGauss)
-        {
-            unsigned int rseed = 66;
-            if (!cp_getvar("rndseed", CP_NUM, &rseed)) {
-                time_t acttime = time(NULL);
-                rseed = (unsigned int) acttime;
-            }
-            srand(rseed);
-            initw();
-        }
+        initw();
 #endif
 
         if (!ft_servermode) {

src/maths/misc/randnumb.c

@@ -2,8 +2,11 @@
 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'.
+   The seed value is obtained from getpid() in main.c upon start-up
+   and stored in a variable named 'rndseed'.
+   A fixed seed value may be set by 'set rndseed=value' in .spiceinit
+   or interactively. This value then is acknowledged by the next call
+   to checkseed().
 */
 
 
@@ -68,9 +71,13 @@ void rgauss(double* py1, double* py2);
 
 
 /* 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 rand or CombLCGTaus.. .
+   in spinit, .spiceinit or in a .control section
+   with integer value > 0. If available, call srand(value).
+   rndseed set in main.c to getpid will be used, if no 'set rndseed=val' is given.
+   Checkseed should be put in front of any call to rand or CombLCGTaus
+   to catch any change of rndseed.
+   Checkseed may not be used to reset the random number generator, if
+   rndseed has not been changed.
 */
 void checkseed(void)
 {
@@ -81,10 +88,10 @@ void checkseed(void)
       if ((newseed > 0) && (oldseed != newseed)) {
          srand((unsigned int)newseed);
          TausSeed();
+         if (oldseed > 0) /* no printout upon start-up */
+             printf("Seed value for random number generator is set to %d\n", 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); */
    }
    
 }
@@ -190,16 +197,18 @@ unsigned int CombLCGTausInt2(void)
 }
 
 
-/***  gauss  ***/
-
+/***  gauss  ***
+ for speed reasons get two values per pass */
 double gauss0(void)
 {
   static bool gliset = TRUE;
   static double glgset = 0.0;
   double fac,r,v1,v2;
   if (gliset) {
+    checkseed();
     do {
-      v1 = drand();  v2 = drand();
+      v1 = 2.0 * CombLCGTaus() - 1.0;
+      v2 = 2.0 * CombLCGTaus() - 1.0;
       r = v1*v1 + v2*v2;
     } while (r >= 1.0);
 /*    printf("v1 %f, v2 %f\n", v1, v2); */
@@ -213,6 +222,24 @@ double gauss0(void)
   }
 }
 
+
+/***  gauss  ***
+  to be reproducible, we just use one value per pass */
+double gauss1(void)
+{
+    double fac, r, v1, v2;
+    checkseed();
+    do {
+        v1 = 2.0 * CombLCGTaus() - 1.0;
+        v2 = 2.0 * CombLCGTaus() - 1.0;
+        r = v1*v1 + v2*v2;
+    } while (r >= 1.0);
+    /*    printf("v1 %f, v2 %f\n", v1, v2); */
+    fac = sqrt(-2.0 * log(r) / r);
+    return v2 * fac;
+}
+
+
 /* Polar form of the Box-Muller generator for Gaussian distributed
    random variates.
    Generator will be fed with two uniformly distributed random variates.
@@ -222,14 +249,14 @@ double gauss0(void)
 void rgauss(double* py1, double* py2)
 {
 	double x1, x2, w;
+    checkseed();
+    do {
+        x1 = 2.0 * CombLCGTaus() - 1.0;
+        x2 = 2.0 * CombLCGTaus() - 1.0;
+        w = x1 * x1 + x2 * x2;
+    } while ( w >= 1.0 );
 
-         do {
-                 x1 = 2.0 * CombLCGTaus() - 1.0;
-                 x2 = 2.0 * CombLCGTaus() - 1.0;
-                 w = x1 * x1 + x2 * x2;
-         } while ( w >= 1.0 );
-
-         w = sqrt( (-2.0 * log( w ) ) / w );
+    w = sqrt( (-2.0 * log( w ) ) / w );
 
 	*py1 = x1 * w;
 	*py2 = x2 * w;
@@ -243,6 +270,7 @@ int poisson(double lambda)
 {
   int k=0;                          //Counter
   const int max_k = 1000;           //k upper limit
+  checkseed();
   double p = CombLCGTaus();         //uniform random number
   double P = exp(-lambda);        //probability
   double sum=P;                     //cumulant

src/sharedspice.c

@@ -582,8 +582,9 @@ ngSpice_Init(SendChar* printfcn, SendStat* statusfcn, ControlledExit* ngspiceexi
     /* program name*/
     cp_program = ft_sim->simulator;
 
-    srand((unsigned int) getpid());
-    TausSeed();
+    int ii = getpid();
+    cp_vset("rndseed", CP_NUM, &ii);
+    checkseed();
 
     /*parameter fetcher, used in show, alter, altermod */
     if_getparam = spif_getparam_special;
@@ -648,15 +649,7 @@ bot:
         fprintf (cp_out, "SoS %f, seed value: %ld\n", renormalize(), rseed);
     }
 #elif defined (WaGauss)
-    {
-        unsigned int rseed = 66;
-        if (!cp_getvar("rndseed", CP_NUM, &rseed)) {
-            time_t acttime = time(NULL);
-            rseed = (unsigned int) acttime;
-        }
-        srand(rseed);
-        initw();
-    }
+    initw();
 #endif
 
 //  com_version(NULL);