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This was an error in the implementation #2336

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This was an error in the implementation #2336

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ea1eb12
This was an error in the implementation
JJ Nov 13, 2024
2a99d94
This simply makes it clearer
JJ Nov 19, 2024
6ced3f6
Put everything on the same line and eliminate unneeded parentheses
JJ Nov 19, 2024
4b3289b
:recycle: to make it even closer to the formula
JJ Nov 19, 2024
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2 changes: 1 addition & 1 deletion code-experiments/src/f_katsuura.c
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Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,7 @@ static double f_katsuura_raw(const double *x, const size_t number_of_variables)
}
/*result = 10. / ((double) number_of_variables) / ((double) number_of_variables)
* (-1. + pow(result, 10. / pow((double) number_of_variables, 1.2)));*/
result = 10. / ((double) number_of_variables) / ((double) number_of_variables)
result = 10. / ((double) number_of_variables) * ((double) number_of_variables)
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@nikohansen nikohansen Nov 14, 2024 •
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this line can be reduced to

result = 10.

because the operations "/ ((double) number_of_variables)" and "* ((double) number_of_variables)" cancel each other out. This lets me believe the original implementation was correct as it did twice "/ ((double) number_of_variables)", am I wrong?

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Not really, it's 1/D^2, as in the formula. The original implementation was simply 1 (in a roundabout way, because looking at code generated it actually did insert the division of D/D)

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Not really, it's 1/D^2, as in the formula. The original implementation was simply 1 (in a roundabout way, because looking at code generated it actually did insert the division of D/D)

I don't know. @JJ, let me ask a questions such that we may be able to get on the same page. What is the result of 10. / 20. / 20. when executed in C?

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OK, I get it now. Operator associativity actually makes 10/20/20 be equivalent to 10/(2020) and 10/2020 be equivalent to (10/20)*20. What I have done is to use parentheses to make the implementation closer to the formula, and prevent people from applying operator precedence and associativity rules, thus reducing cognitive load.

* (-1. + result);

return result;
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