Is rsqrt the same as Fast inverse square root?
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Edited: Walter Roberson on 31 Jul 2022
I would like to us sqrt() and run it on a embeded controller. I was wondering sqrt() is the same as Fast inverse square root ( https://en.wikipedia.org/wiki/Fast_inverse_square_root ). if not, is it efficent as Fast inverse square root. Does it support code generation? Can I use it in embeded control software?
stozaki on 13 Sep 2021
The Simulink sqrt block supports rsqrt.
The algorithm is Newton-Raphson, so it can be considered the same as the one described on the wiki.
With that setting, C code generation is possible.
More Answers (1)
Jan on 13 Sep 2021
i = * ( long * ) &y
This is equivalent to:
y = single(pi);
i = typecast(y, 'int32');
The shown code of Q_rsqrt is an approximation of 1/sqrt(x) for single precision floating point values. It might have a fair speed on CPUs without a floating point unit, but it is less accurate then the direct calculation.
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