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/* -------------------------------------------------------------- */ /* (C)Copyright 2007,2008, */ /* International Business Machines Corporation */ /* All Rights Reserved. */ /* */ /* Redistribution and use in source and binary forms, with or */ /* without modification, are permitted provided that the */ /* following conditions are met: */ /* */ /* - Redistributions of source code must retain the above copyright*/ /* notice, this list of conditions and the following disclaimer. */ /* */ /* - Redistributions in binary form must reproduce the above */ /* copyright notice, this list of conditions and the following */ /* disclaimer in the documentation and/or other materials */ /* provided with the distribution. */ /* */ /* - Neither the name of IBM Corporation nor the names of its */ /* contributors may be used to endorse or promote products */ /* derived from this software without specific prior written */ /* permission. */ /* */ /* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND */ /* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, */ /* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF */ /* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE */ /* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR */ /* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, */ /* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT */ /* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; */ /* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) */ /* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN */ /* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR */ /* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, */ /* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ /* -------------------------------------------------------------- */ /* PROLOG END TAG zYx */ #ifdef __SPU__ #ifndef _ERFD2_H_ #define _ERFD2_H_ 1 #include <spu_intrinsics.h> #include "expd2.h" #include "recipd2.h" #include "divd2.h" #include "erf_utils.h" /* * FUNCTION * vector double _erfd2(vector double x) * * DESCRIPTION * The erfd2 function computes the error function of each element of x. * * C99 Special Cases: * - erf(+0) returns +0 * - erf(-0) returns -0 * - erf(+infinite) returns +1 * - erf(-infinite) returns -1 * * Other Cases: * - erf(Nan) returns Nan * */ static __inline vector double _erfd2(vector double x) { vec_uchar16 dup_even = ((vec_uchar16) { 0,1,2,3, 0,1,2,3, 8, 9,10,11, 8, 9,10,11 }); vec_double2 onehalfd = spu_splats(0.5); vec_double2 oned = spu_splats(1.0); vec_double2 sign_mask = spu_splats(-0.0); /* This is where we switch from Taylor Series to Continued Fraction approximation */ vec_float4 approx_point = spu_splats(1.77f); vec_double2 xabs, xsqu, xsign; vec_double2 tresult, presult, result; xsign = spu_and(x, sign_mask); xabs = spu_andc(x, sign_mask); xsqu = spu_mul(x, x); /* * Taylor Series Expansion near Zero */ TAYLOR_ERF(xabs, xsqu, tresult); /* * Continued Fraction Approximation of Erfc(). * erf = 1 - erfc */ CONTFRAC_ERFC(xabs, xsqu, presult); presult = spu_sub(oned, presult); /* * Select the appropriate approximation. */ vec_float4 xf = spu_roundtf(xabs); xf = spu_shuffle(xf, xf, dup_even); result = spu_sel(tresult, presult, (vec_ullong2)spu_cmpgt(xf, approx_point)); /* * Special cases/errors. */ /* x = +/- infinite, return +/-1 */ /* x = nan, return x */ result = spu_sel(result, oned, spu_testsv(x, SPU_SV_NEG_INFINITY | SPU_SV_POS_INFINITY)); result = spu_sel(result, x, spu_testsv(x, SPU_SV_NEG_DENORM | SPU_SV_POS_DENORM)); /* * Preserve sign in result, since erf(-x) = -erf(x) */ result = spu_or(result, xsign); return result; } #endif /* _ERFD2_H_ */ #endif /* __SPU__ */