| 1 | /* -------------------------------------------------------------- */ |
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| 2 | /* (C)Copyright 2007,2008, */ |
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| 3 | /* International Business Machines Corporation */ |
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| 4 | /* All Rights Reserved. */ |
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| 5 | /* */ |
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| 6 | /* Redistribution and use in source and binary forms, with or */ |
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| 7 | /* without modification, are permitted provided that the */ |
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| 8 | /* following conditions are met: */ |
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| 9 | /* */ |
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| 10 | /* - Redistributions of source code must retain the above copyright*/ |
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| 11 | /* notice, this list of conditions and the following disclaimer. */ |
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| 12 | /* */ |
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| 13 | /* - Redistributions in binary form must reproduce the above */ |
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| 14 | /* copyright notice, this list of conditions and the following */ |
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| 15 | /* disclaimer in the documentation and/or other materials */ |
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| 16 | /* provided with the distribution. */ |
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| 17 | /* */ |
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| 18 | /* - Neither the name of IBM Corporation nor the names of its */ |
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| 19 | /* contributors may be used to endorse or promote products */ |
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| 20 | /* derived from this software without specific prior written */ |
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| 21 | /* permission. */ |
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| 22 | /* */ |
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| 23 | /* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND */ |
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| 24 | /* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, */ |
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| 25 | /* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF */ |
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| 26 | /* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE */ |
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| 27 | /* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR */ |
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| 28 | /* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, */ |
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| 29 | /* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT */ |
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| 30 | /* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; */ |
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| 31 | /* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) */ |
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| 32 | /* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN */ |
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| 33 | /* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR */ |
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| 34 | /* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, */ |
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| 35 | /* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ |
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| 36 | /* -------------------------------------------------------------- */ |
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| 37 | /* PROLOG END TAG zYx */ |
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| 38 | #ifdef __SPU__ |
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| 39 | #ifndef _TANHF4_H_ |
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| 40 | #define _TANHF4_H_ 1 |
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| 41 | |
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| 42 | #include <spu_intrinsics.h> |
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| 43 | |
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| 44 | #include "expf4.h" |
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| 45 | #include "divf4.h" |
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| 46 | |
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| 47 | #include "tanhd2.h" |
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| 48 | |
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| 49 | /* |
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| 50 | * FUNCTION |
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| 51 | * vector float _tanhf4(vector float x) |
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| 52 | * |
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| 53 | * DESCRIPTION |
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| 54 | * The _tanhf4 function computes the hyperbolic tangent for each |
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| 55 | * element of the input vector. |
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| 56 | * |
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| 57 | * We use the following to approximate tanh: |
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| 58 | * |
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| 59 | * |x| <= .25: Taylor Series |
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| 60 | * |x| > .25: tanh(x) = (exp(2x) - 1)/(exp(2x) + 1) |
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| 61 | * |
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| 62 | * |
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| 63 | * SPECIAL CASES: |
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| 64 | * - tanh(+/- 0) = +/-0 |
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| 65 | * - tanh(+/- infinity) = +/- 1 |
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| 66 | * |
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| 67 | */ |
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| 68 | |
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| 69 | static __inline vector float _tanhf4(vector float x) |
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| 70 | { |
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| 71 | vector float signbit = spu_splats(-0.0f); |
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| 72 | vector float onef = spu_splats(1.0f); |
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| 73 | vector float twof = spu_splats(2.0f); |
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| 74 | vector float xabs; |
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| 75 | vector float x2; |
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| 76 | vector unsigned int gttaylor; |
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| 77 | vector float e; |
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| 78 | vector float tresult; |
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| 79 | vector float eresult; |
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| 80 | vector float result; |
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| 81 | |
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| 82 | xabs = spu_andc(x, signbit); |
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| 83 | |
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| 84 | /* |
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| 85 | * This is where we switch from Taylor Series |
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| 86 | * to exponential formula. |
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| 87 | */ |
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| 88 | gttaylor = spu_cmpgt(xabs, spu_splats(0.25f)); |
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| 89 | |
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| 90 | |
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| 91 | /* |
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| 92 | * Taylor Series Approximation |
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| 93 | */ |
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| 94 | x2 = spu_mul(x,x); |
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| 95 | tresult = spu_madd(x2, spu_splats((float)TANH_TAY06), spu_splats((float)TANH_TAY05)); |
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| 96 | tresult = spu_madd(x2, tresult, spu_splats((float)TANH_TAY04)); |
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| 97 | tresult = spu_madd(x2, tresult, spu_splats((float)TANH_TAY03)); |
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| 98 | tresult = spu_madd(x2, tresult, spu_splats((float)TANH_TAY02)); |
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| 99 | tresult = spu_madd(x2, tresult, spu_splats((float)TANH_TAY01)); |
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| 100 | tresult = spu_mul(xabs, tresult); |
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| 101 | |
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| 102 | |
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| 103 | /* |
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| 104 | * Exponential Formula |
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| 105 | * Our expf4 function gives a more accurate result in general |
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| 106 | * with xabs instead of x for x<0. We correct for sign later. |
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| 107 | */ |
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| 108 | e = _expf4(spu_mul(xabs, twof)); |
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| 109 | eresult = _divf4(spu_sub(e, onef), spu_add(e, onef)); |
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| 110 | |
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| 111 | |
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| 112 | /* |
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| 113 | * Select Taylor or exp result. |
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| 114 | */ |
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| 115 | result = spu_sel(tresult, eresult, gttaylor); |
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| 116 | |
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| 117 | /* |
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| 118 | * Correct for accumulated truncation error when |
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| 119 | * tanh(x) should return 1. |
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| 120 | * Note that this also handles the special case of |
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| 121 | * x = +/- infinity. |
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| 122 | */ |
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| 123 | result = spu_sel(result, onef, spu_cmpgt(xabs, spu_splats(9.125f))); |
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| 124 | |
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| 125 | /* |
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| 126 | * Antisymmetric function - preserve sign bit of x |
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| 127 | * in the result. |
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| 128 | */ |
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| 129 | result = spu_sel(result, x, (vec_uint4)signbit); |
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| 130 | |
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| 131 | return result; |
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| 132 | } |
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| 133 | |
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| 134 | #endif /* _TANHF4_H_ */ |
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| 135 | #endif /* __SPU__ */ |
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