added skip8 method

ChangeLog

@@ -28,6 +28,8 @@ Version NEXT
 	randomcheck: ability to run group tests with different seeds
 	  this will more balance results to be less initial seed
 	  dependant. classic fsp algo seems to produce best results.
+	randomcheck: added skip8 method. skips 8 lowest bits from
+	  random() output
 
 Version 2.8.1b29 - 24 Aug 2019
 	added scons command line argument without-fspscan=yes for building

tests/randomcheck.c

@@ -4,7 +4,8 @@
 #include "my-string.h"
 #include <math.h>
 
-static int group[4];
+#define GROUPS 5
+static int group[GROUPS];
 static int bitcount[16];
 static int rounds;
 static int groups;
@@ -46,6 +47,10 @@ static unsigned short simple2 (void)
   /* we assume that our return value is 16 bits long
      and random() returns only positive long integers
   */
+  /* TODO: this needs to be checked on 64-bit systems because
+     I am not sure if random returns 31 bits or 63 bits of
+     randomness there.
+  */
   return ( random() >> (SIZEOF_LONG*8 - 16 - 1) );
 }
 
@@ -57,6 +62,13 @@ static unsigned short nr(void)
         return(ulRandom);
 }
 
+/* Skip lowest 8 bits */
+static unsigned short skip8(void)
+{
+        long randomValue = random();
+        return randomValue >> 8;
+}
+
 static void run_randomtest( unsigned short (*keygen)(void) )
 {
     int i,j;
@@ -88,9 +100,9 @@ static void print_bitcount(void)
     for(i=0;i<16;i++)
     {
         float ratio;
-	float delta;
+        float delta;
         ratio=(float)bitcount[i]/rounds;
-	delta = fabs(ratio-0.5f);
+        delta = fabs(ratio-0.5f);
         if(delta > worst)
             worst=delta;
         printf("%.2f ", ratio);
@@ -107,9 +119,9 @@ static float worst_bitcount(void)
     for(i=0;i<16;i++)
     {
         float ratio;
-	float delta;
+        float delta;
         ratio=(float)bitcount[i]/rounds;
-	delta = fabs(ratio-0.5f);
+        delta = fabs(ratio-0.5f);
         if(delta > worst)
             worst=delta;
     }
@@ -118,7 +130,7 @@ static float worst_bitcount(void)
 
 static void run_one(void)
 {
-    float worst[4];
+    float worst[GROUPS];
     memset(worst, 0, sizeof(worst));
 
     run_randomtest(classic);
@@ -133,16 +145,19 @@ static void run_one(void)
     run_randomtest(nr);
     worst[3] = worst_bitcount();
 
+    run_randomtest(skip8);
+    worst[4] = worst_bitcount();
+
     /* fimd the best algo */
     float minValue = worst[0];
     int minIndex = 0;
 
-    for (int i = 1; i < 4; i++)
+    for (int i = 1; i < GROUPS; i++)
     {
        if (worst[i] < minValue)
        {
           minValue = worst[i];
-	  minIndex = i;
+          minIndex = i;
        }
     }
 
@@ -180,35 +195,36 @@ int main(int argc,const char *argv[])
 
     if ( groups == 1 )
     {
-	seed_rng();
+        seed_rng();
-	printf("Generator: classic\n");
+        printf("Generator: classic\n");
-	run_randomtest(classic);
+        run_randomtest(classic);
-	print_bitcount();
+        print_bitcount();
 
-	printf("Generator: simple (low bits)\n");
+        printf("Generator: simple (low bits)\n");
-	run_randomtest(simple);
+        run_randomtest(simple);
-	print_bitcount();
+        print_bitcount();
 
-	printf("Generator: simple2 (high bits)\n");
+        printf("Generator: simple2 (high bits)\n");
-	run_randomtest(simple2);
+        run_randomtest(simple2);
-	print_bitcount();
+        print_bitcount();
 
-	printf("Generator: Numerical Recipes\n");
+        printf("Generator: Numerical Recipes\n");
-	run_randomtest(nr);
+        run_randomtest(nr);
-	print_bitcount();
+        print_bitcount();
     } else {
-	int i;
+        int i;
-	for (i=0; i< groups; i++)
+        for (i=0; i< groups; i++)
-	{
+        {
-	   seed_rng();
+           seed_rng();
-	   run_one();
+           run_one();
-	}
+        }
 
-	printf("Winning generators\n\n");
+        printf("Winning generators\n\n");
-	printf("Generator: classic %d\n", group[0]);
+        printf("Generator: classic %d\n", group[0]);
-	printf("Generator: simple (low bits) %d\n", group[1]);
+        printf("Generator: simple (low bits) %d\n", group[1]);
-	printf("Generator: simple2 (high bits) %d\n", group[2]);
+        printf("Generator: simple2 (high bits) %d\n", group[2]);
-	printf("Generator: Numerical Recipes %d\n", group[3]);
+        printf("Generator: Numerical Recipes %d\n", group[3]);
+        printf("Generator: skip8 (skip 8 lower bits) %d\n", group[4]);
     }
 
     return result;