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91 lines
3.1 KiB
91 lines
3.1 KiB
4 months ago
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/*
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* Copyright (c) 2014,2015 Advanced Micro Devices, Inc.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include <clc/clc.h>
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#include "math.h"
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#include "../clcmacro.h"
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_CLC_OVERLOAD _CLC_DEF float exp(float x) {
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// Reduce x
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const float ln2HI = 0x1.62e300p-1f;
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const float ln2LO = 0x1.2fefa2p-17f;
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const float invln2 = 0x1.715476p+0f;
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float fhalF = x < 0.0f ? -0.5f : 0.5f;
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int p = mad(x, invln2, fhalF);
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float fp = (float)p;
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float hi = mad(fp, -ln2HI, x); // t*ln2HI is exact here
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float lo = -fp*ln2LO;
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// Evaluate poly
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float t = hi + lo;
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float tt = t*t;
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float v = mad(tt,
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-mad(tt,
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mad(tt,
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mad(tt,
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mad(tt, 0x1.637698p-25f, -0x1.bbd41cp-20f),
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0x1.1566aap-14f),
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-0x1.6c16c2p-9f),
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0x1.555556p-3f),
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t);
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float y = 1.0f - (((-lo) - MATH_DIVIDE(t * v, 2.0f - v)) - hi);
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// Scale by 2^p
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float r = as_float(as_int(y) + (p << 23));
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const float ulim = 0x1.62e430p+6f; // ln(largest_normal) = 88.72283905206835305366
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const float llim = -0x1.5d589ep+6f; // ln(smallest_normal) = -87.33654475055310898657
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r = x < llim ? 0.0f : r;
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r = x < ulim ? r : as_float(0x7f800000);
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return isnan(x) ? x : r;
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}
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_CLC_UNARY_VECTORIZE(_CLC_OVERLOAD _CLC_DEF, float, exp, float)
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#ifdef cl_khr_fp64
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#include "exp_helper.h"
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#pragma OPENCL EXTENSION cl_khr_fp64 : enable
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_CLC_OVERLOAD _CLC_DEF double exp(double x) {
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const double X_MIN = -0x1.74910d52d3051p+9; // -1075*ln(2)
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const double X_MAX = 0x1.62e42fefa39efp+9; // 1024*ln(2)
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const double R_64_BY_LOG2 = 0x1.71547652b82fep+6; // 64/ln(2)
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const double R_LOG2_BY_64_LD = 0x1.62e42fefa0000p-7; // head ln(2)/64
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const double R_LOG2_BY_64_TL = 0x1.cf79abc9e3b39p-46; // tail ln(2)/64
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int n = convert_int(x * R_64_BY_LOG2);
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double r = fma(-R_LOG2_BY_64_TL, (double)n, fma(-R_LOG2_BY_64_LD, (double)n, x));
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return __clc_exp_helper(x, X_MIN, X_MAX, r, n);
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}
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_CLC_UNARY_VECTORIZE(_CLC_OVERLOAD _CLC_DEF, double, exp, double)
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#endif
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