-----BEGIN PGP SIGNED MESSAGE----- jws@neon.netscape.com writes:
Most of the unix machines do the same thing. On SGI machines that have the hardware cycle counter, its value is used in place of the srand48(usec), lrand48() sequence. BSDI the code used srandom and random.
Kun Luo, one of our grad students here recently found a bug in Sun's implemen- tation of the drand48() function. We reported it to Sun, and they acknowledged the bug exists - it seemed to be the first time they had heard of it, though. The bug affects Sun's ANSI C compiler shipped with SPARCWorks3.0 and consists of the following: If you're compiling using the - -Xc flag (strict ANSI C, no SUN C compatibility extensions), the function drand48() is BROKEN. It ALWAYS returns the number 9.000000, no matter what you seeded it with using srand48(). to reproduce, compile the following program under Solaris 2.x using their C compiler AND the -Xc flag: #include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <time.h> void main(){ double number; int num = 1000; srand48((int)time(NULL)); while(num --){ number = drand48(); printf("%lf\n", number); } } By the way, Cyphepunks mail seems to indicate that Netscape uses lrand48() instead of drand48(). lrand48() is NOT broken. The potential for disaster is high, though, for anyone blindly trusting vendor-provided pseudo- random number generators. How many products are out there using drand48() as part of their random number generation scheme? - -Arve - -----BEGIN PGP PUBLIC KEY BLOCK----- Version: 2.6.2 mQCNAzAvqdwAAAEEAKRdBFn7O/h+wz3tOQwHWvaFKS6gi+UezzCXli/QnuCrJcUE agvlVVZ/PzKG5i23VdbghyHsVElvKzRW/D1pYor6xSluCftXzSxbCuiEIe2SXUsH 65AqFN688upXzRKHcq3bU/eKB7xUOGqCDot8AzModnwE+XWCgdqn8CTZCNGhAAUR tCJBcnZlIEtqb2VsZW4gPGFram9lbGVAZWUuc2l1ZS5lZHU+ =csFb - -----END PGP PUBLIC KEY BLOCK----- -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCUAwUBMGAusNqn8CTZCNGhAQEYdQP4+UGvLJKoQPWPLFMENDIPY1QSIuQdQxdt fTzWRNXsPadE4N40bHgucqZQG8Ze55JsKIrrhL9RZFIVx+ygxsmsSHsocu/kFbSW E7RNWMvoaoRAmB4KkWF+ofqRWl9Qo+r00CvgX1brsOdpjySVIkxml8/L7R/RBuQL aFNV5OBz2w== =saUT -----END PGP SIGNATURE-----