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awk: improve random number generation

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don't use rand() and scale it to 0..1, instead call
native frand() which produces uniform random number.

instead of seeding the rng with time(0), use truerand().
This commit is contained in:
cinap_lenrek 2016-12-18 18:00:45 +01:00
parent 2830cd7eb6
commit 4f72cda4ac
1 changed files with 2 additions and 7 deletions
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9
sys/src/cmd/awk/run.c
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@ -29,10 +29,6 @@ THIS SOFTWARE.
#include "awk.h"
#include "y.tab.h"
#ifndef RAND_MAX
#define RAND_MAX 32767 /* all that ansi guarantees */
#endif
jmp_buf env;
extern int pairstack[];
@ -1582,12 +1578,11 @@ Cell *bltin(Node **a, int) /* builtin functions. a[0] is type, a[1] is arg list
u = (Awkfloat) system(getsval(x));
break;
case FRAND:
/* in principle, rand() returns something in 0..RAND_MAX */
u = (Awkfloat) (rand() % RAND_MAX) / RAND_MAX;
u = frand();
break;
case FSRAND:
if (isrec(x)) /* no argument provided */
u = time(nil);
u = (Awkfloat) (truerand() >> 1);
else
u = getfval(x);
srand((unsigned int) u);