command.c, add command 'setseed'

randnumb.c, add function com_sseed
for immediately setting the seed of the random number generator
'setseed' uses variable rndseed as seed
'setseed <n>' uses <n> as seed and sets rndseed to <n>

src/frontend/commands.c

@@ -83,6 +83,7 @@
 #include "resource.h"
 #include "diff.h"
 #include "com_strcmp.h"
+#include "ngspice/randnumb.h"
 
 #include "arg.h"
 
@@ -193,6 +194,10 @@ struct comm spcp_coms[] = {
       { 040000, 0, 0, 0 }, E_DEFHMASK, 0, 1,
       NULL,
       "[vecname] : Change default scale of current working plot." } ,
+    { "setseed", com_sseed, FALSE, FALSE,
+      { 04, 0, 0, 0 }, E_DEFHMASK, 0, 1,
+      NULL,
+      "[seed value] : Reset the random number generator with new seed value." } ,
     { "transpose", com_transpose, FALSE, FALSE,
       { 040000, 040000, 040000, 040000 }, E_DEFHMASK, 1, LOTS,
       NULL,
@@ -666,6 +671,10 @@ struct comm nutcp_coms[] = {
       { 040000, 0, 0, 0 }, E_DEFHMASK, 0, 1,
       NULL,
       "[vecname] : Change default scale of current working plot." } ,
+    { "setseed", com_sseed, FALSE, FALSE,
+      { 04, 0, 0, 0 }, E_DEFHMASK, 0, 1,
+      NULL,
+      "[seed value] : Reset therandom number generator with new seed value." } ,
     { "transpose", com_transpose, FALSE, FALSE,
       { 040000, 040000, 040000, 040000 }, E_DEFHMASK, 1, LOTS,
       NULL,

src/include/ngspice/randnumb.h

@@ -1,6 +1,9 @@
 #ifndef ngspice_RANDNUMB_H
 #define ngspice_RANDNUMB_H
 
+#include "ngspice/wordlist.h"
+extern void com_sseed(wordlist *wl);
+
 /* initialize random number generators */
 extern void initw(void);
 

src/maths/misc/randnumb.c

@@ -292,3 +292,35 @@ double exprand(double mean)
     expval = -log(CombLCGTaus()) * mean;
     return expval;
 }
+
+
+/* seed random number generators immediately
+* command "setseed"
+*   take value of variable rndseed as seed
+* command "setcirc <n>"
+*   seed with number <n>
+*/
+void
+com_sseed(wordlist *wl)
+{
+    int newseed;
+
+    if (wl == NULL) {
+        if (!cp_getvar("rndseed", CP_NUM, &newseed)) {
+            newseed = getpid();
+            cp_vset("rndseed", CP_NUM, &newseed);
+        }
+        srand((unsigned int)newseed);
+        TausSeed();
+    }
+    else
+        if ((sscanf(wl->wl_word, " %d ", &newseed) != 1) || (newseed <= 0) || (newseed > INT_MAX)) {
+            fprintf(cp_err, "Warning: Cannot use %s as seed!\n\n", wl->wl_word);
+            return;
+        }
+        else {
+            srand((unsigned int)newseed);
+            TausSeed();
+        }
+    printf("\nSeed value for random number generator is set to %d\n", newseed);
+}