Unbias a random generator: Difference between revisions
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The actual unbiasing should be done by generating two numbers at a time from randN and only returning a 1 or 0 if they are different. As long as you always return the first number or always return the second number, the probabilities discussed above should take over the biased probability of randN. |
The actual unbiasing should be done by generating two numbers at a time from randN and only returning a 1 or 0 if they are different. As long as you always return the first number or always return the second number, the probabilities discussed above should take over the biased probability of randN. |
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=={{header|C}}== |
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<lang C>#include <stdio.h> |
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#include <stdlib.h> |
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int biased(int bias) |
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{ |
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/* balance out the bins, being pedantic */ |
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int r, rand_max = RAND_MAX - (RAND_MAX % bias); |
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while ((r = rand()) > rand_max); |
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return rand() < rand_max / bias; |
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} |
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int unbiased(int bias) |
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{ |
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int a; |
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while ((a = biased(bias)) == biased(bias)); |
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return a; |
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} |
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int main() |
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{ |
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int b, n = 10000, cb, cu, i; |
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for (b = 3; b <= 6; b++) { |
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for (i = cb = cu = 0; i < n; i++) { |
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cb += biased(b); |
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cu += unbiased(b); |
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} |
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printf("bias %d: %5d %5.3f%% vs %5d %5.3f\n", b, |
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cb, 100. * cb / n, cu, 100. * cu / n); |
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} |
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return 0; |
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}</lang>output<lang>bias 3: 3309 33.090% vs 4971 49.710 |
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bias 4: 2513 25.130% vs 4943 49.430 |
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bias 5: 1976 19.760% vs 4965 49.650 |
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bias 6: 1674 16.740% vs 5003 50.030</lang> |
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=={{header|Clojure}}== |
=={{header|Clojure}}== |
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<lang Clojure>(defn biased [n] |
<lang Clojure>(defn biased [n] |
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