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/*
* There are multiple formulas for calculating arccosine of x:
* 1) acos(x) = (1/2*pi) + i * ln(i*x + sqrt(1-x^2)) (notice the 'i'...)
* 2) acos(x) = pi/2 + asin(-x) (asin isn't implemented yet)
* 3) acos(x) = pi/2 - asin(x) (ditto)
* 4) acos(x) = 2*atan2(sqrt(1-x), sqrt(1+x))
* 5) acos(x) = pi/2 - atan2(x, ( sqrt(1-x^2) ) )
*
* Options 1-3 are not currently usable, #5 generates more concise radeonsi
* bitcode and assembly than #4 (134 vs 132 instructions on radeonsi), but
* precision of #4 may be better.
*/
#if __CLC_FPSIZE == 32
#define __CLC_CONST(x) x ## f
#else
#define __CLC_CONST(x) x
#endif
_CLC_OVERLOAD _CLC_DEF __CLC_GENTYPE acos(__CLC_GENTYPE x) {
return (
(__CLC_GENTYPE) __CLC_CONST(2.0) * atan2(
sqrt((__CLC_GENTYPE) __CLC_CONST(1.0) - x),
sqrt((__CLC_GENTYPE) __CLC_CONST(1.0) + x)
)
);
}
#undef __CLC_CONST
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