[LC++]Random numbers

[Mark Phillips]

Hi,

Doing "man 3 rand" on a linux system gives the following information
about random number generation:

       The  versions of rand() and srand() in the Linux C Library
       use the same  random  number  generator  as  random()  and
       srandom(),  so the lower-order bits should be as random as
       the  higher-order  bits.    However,   on   older   rand()
       implementations, the lower-order bits are much less random
       than the higher-order bits.

       In Numerical Recipes in C: The Art of Scientific Computing
       (William  H.  Press, Brian P. Flannery, Saul A. Teukolsky,
       William T.  Vetterling;  New  York:  Cambridge  University
       Press, 1992 (2nd ed., p. 277)), the following comments are
       made:
              "If you want to generate a random integer between 1
              and 10, you should always do it by using high-order
              bits, as in

                     j=1+(int) (10.0*rand()/(RAND_MAX+1.0));

              and never by anything resembling

                     j=1+(rand() % 10);

              (which uses lower-order bits)."

Is the comment from Numerical Recipes in C based on older versions
of rand()?  Ie is it that the first method above (of generating
a number between 1 and 10) used to be preferable to the second
method, but now with improved random number generators, the
second method is just as good --- (and quicker!)??

Thanks,

Mark.