123 lines
5.4 KiB
C
123 lines
5.4 KiB
C
/* -------------------------------------------------------------- */
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/* (C)Copyright 2006,2008, */
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/* International Business Machines Corporation */
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/* All Rights Reserved. */
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/* */
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/* Redistribution and use in source and binary forms, with or */
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/* without modification, are permitted provided that the */
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/* following conditions are met: */
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/* */
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/* - Redistributions of source code must retain the above copyright*/
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/* notice, this list of conditions and the following disclaimer. */
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/* */
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/* - Redistributions in binary form must reproduce the above */
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/* copyright notice, this list of conditions and the following */
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/* disclaimer in the documentation and/or other materials */
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/* provided with the distribution. */
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/* */
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/* - Neither the name of IBM Corporation nor the names of its */
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/* contributors may be used to endorse or promote products */
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/* derived from this software without specific prior written */
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/* permission. */
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/* */
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/* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND */
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/* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, */
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/* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF */
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/* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE */
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/* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR */
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/* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, */
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/* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT */
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/* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; */
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/* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) */
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/* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN */
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/* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR */
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/* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, */
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/* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
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/* -------------------------------------------------------------- */
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/* PROLOG END TAG zYx */
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#ifdef __SPU__
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#ifndef _HYPOTD2_H_
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#define _HYPOTD2_H_ 1
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#include <spu_intrinsics.h>
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#include "sqrtd2.h"
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/*
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* FUNCTION
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* vector double hypotd2(vector double x, vector double y)
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*
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* DESCRIPTION
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* The function hypotd2 returns a double vector in which each element is
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* the square root of the sum of the squares of the corresponding
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* elements of x and y.
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*
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* The purpose of this function is to avoid overflow during
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* intermediate calculations, and therefore it is slower than
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* simply calcualting sqrt(x^2 + y^2).
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*
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* This function is performed by factoring out the larger of the 2
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* input exponents and moving this factor outside of the sqrt calculation.
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* This will minimize the possibility of over/underflow when the square
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* of the values are calculated. Think of it as normalizing the larger
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* input to the range [1,2).
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*
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* Special Cases:
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* - hypot(x, +/-0) returns |x|
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* - hypot(+/- infinity, y) returns +infinity
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* - hypot(+/- infinity, NaN) returns +infinity
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*
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*/
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static __inline vector double _hypotd2(vector double x, vector double y)
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{
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vector unsigned long long emask = spu_splats(0x7FF0000000000000ull);
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vector unsigned long long mmask = spu_splats(0x000FFFFFFFFFFFFFull);
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vector signed long long bias = spu_splats(0x3FF0000000000000ll);
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vector double oned = spu_splats(1.0);
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vector double sbit = spu_splats(-0.0);
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vector double inf = (vector double)spu_splats(0x7FF0000000000000ull);
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vector double max, max_e, max_m;
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vector double min, min_e, min_m;
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vector unsigned long long xgty;
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vector double sum;
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vector double result;
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/* Only need absolute values for this function */
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x = spu_andc(x, sbit);
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y = spu_andc(y, sbit);
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xgty = spu_cmpgt(x,y);
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max = spu_sel(y,x,xgty);
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min = spu_sel(x,y,xgty);
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/* Extract the exponents and mantissas */
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max_e = (vec_double2)spu_and((vec_ullong2)max, emask);
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max_m = (vec_double2)spu_and((vec_ullong2)max, mmask);
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min_e = (vec_double2)spu_and((vec_ullong2)min, emask);
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min_m = (vec_double2)spu_and((vec_ullong2)min, mmask);
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/* Factor-out max exponent here by subtracting from min exponent */
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vec_llong2 min_e_int = (vec_llong2)spu_sub((vec_int4)min_e, (vec_int4)max_e);
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min_e = (vec_double2)spu_add((vec_int4)min_e_int, (vec_int4)bias);
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/* If the new min exponent is too small, just set it to 0. It
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* wouldn't contribute to the final result in either case.
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*/
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min_e = spu_sel(min_e, sbit, spu_cmpgt(sbit, min_e));
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/* Combine new exponents with original mantissas */
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max = spu_or(oned, max_m);
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min = spu_or(min_e, min_m);
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sum = _sqrtd2(spu_madd(max, max, spu_mul(min, min)));
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sum = spu_mul(max_e, sum);
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/* Special case: x = +/- infinity */
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result = spu_sel(sum, inf, spu_cmpeq(x, inf));
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return result;
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}
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#endif /* _HYPOTD2_H_ */
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#endif /* __SPU__ */
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