No. Perl's rand() is documented to be completely repeatable when given the same starting point (see srand). So the number of strings possible using just rand() is bound by roughly 2 ** (the number random bits) or, more correctly, the number of effectively different srand() values.

Update: And every implementation that I've seen uses a simple LCPRNG (Linear Congruential Psuedo-Random Number Generator). So each has a fixed number of possible values and it will simply cycle through those in the exact same order each time if you actually call it 2**$bits times. The number of effectively different seed values is called the "period".

Update: Oh, forgot to mention that some implementations intentionally use only a subset of the (upper) bits so the period can often be much higher than 2**$bits. For example, a period of 2**32 is quite common while many such implementations only use 16 bits of each result. And I'm not completely sure, in such a case, whether Perl Config reports that as 16 or 32 "random bits".

Note: Just FYI, the above two updates were posted within a few minutes of the original submission (and thus nearly 2 hours before the first reply).

- tye        

In reply to Re^3: How likely is rand() to repeat? (srand) by tye
in thread How likely is rand() to repeat? by desertrat

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.