Fastest way to clamp a real (fixed/floating point) value?

Posted by Niklas on Stack Overflow See other posts from Stack Overflow or by Niklas
Published on 2009-01-09T09:13:11Z Indexed on 2010/03/21 15:31 UTC
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Hi, Is there a more efficient way to clamp real numbers than using if statements or ternary operators? I want to do this both for doubles and for a 32-bit fixpoint implementation (16.16). I'm not asking for code that can handle both cases; they will be handled in separate functions.

Obviously, I can do something like:

double clampedA;
double a = calculate();
clampedA = a > MY_MAX ? MY_MAX : a;
clampedA = a < MY_MIN ? MY_MIN : a;

or

double a = calculate();
double clampedA = a;
if(clampedA > MY_MAX)
    clampedA = MY_MAX;
else if(clampedA < MY_MIN)
    clampedA = MY_MIN;

The fixpoint version would use functions/macros for comparisons.

This is done in a performance-critical part of the code, so I'm looking for an as efficient way to do it as possible (which I suspect would involve bit-manipulation)

EDIT: It has to be standard/portable C, platform-specific functionality is not of any interest here. Also, MY_MIN and MY_MAX are the same type as the value I want clamped (doubles in the examples above).

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