Strange bug

[jalex]

I just found an extremely odd bug appearing in a model of mine, and I
was hoping the excellent programmers who frequent this list might help
me track it down.


I have the following chunk of code in a model:

  if (max_score > score ) {
    new_strategy = RANDOM_POP(better_strategies, count);
    printf ("Max score: %g, my score: %g\n", 
            max_score, [self getScore]);
  }
  else
    new_strategy = [self getStrategy];


>From time to time, I get lines like the following being printed on-screen:

     Max score: 5.7, my score: 5.7

My question: if max_score == 5.7 and score == 5.7, why on earth is the
printf being called?  Is this an insidious roundoff error?

If it is a roundoff error, could someone please explain (or send a
reference of where I should look for) why my computer thinks

(1.9 + 1.9 + 1.9) != (1.0 + 1.0 + 1.0 + 1.0 + 1.0 + 1.0 - .1 - .1 - .1)

since this is what must happen.


Thanks,

Jason

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