Well, since you said you're going to do this thousands of times... 
use Inline C =>;

print UniqueCount("0101010101"), "\n";
print UniqueCount("1234567812"), "\n";

__END__
__C__

int UniqueCount(unsigned char *str) {
  char counts[256];
  int i;
  int result;

  /* clear the array */

  for (i = 0; i <= 255; i++) {
    counts[i] = (char) 0;
  }

  /* notice the characters */

  while (*str) {
    counts[*str++] = 1;
  }

  /* now count the results */

  result = 0;
  for (i = 0; i <= 255; i++) {
    result += counts[i];
  }

  return result;
}

[download]
Apologies for my rusty C... I've been coding in Perl too long (however, it worked on the first compile!).

-- Randal L. Schwartz, Perl hacker
Be sure to read my standard disclaimer if this is a reply.

In reply to •Re: number of unique characters in a string by merlyn
in thread number of unique characters in a string by Anonymous Monk

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.