72 lines
1.6 KiB
C
72 lines
1.6 KiB
C
/* Copyright 2018 Canaan Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "fastexp.h"
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#include <stdint.h>
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static inline float _fast_exp2f(float in)
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{
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static const float p1 = 0.0f;
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static const float p2 = 0.0f;
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static const float p3 = 0.0f;
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static const float p4 = 0.0f;
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static const float p5 = 0.0f;
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float x1 = in;
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float x2 = x1 * in;
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float x3 = x2 * in;
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float x4 = x3 * in;
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return x4 * p1 + x3 * p2 + x2 * p3 + x1 * p4 + p5;
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}
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float fast_exp2f(float x)
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{
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union _float {
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float f;
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struct {
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uint32_t frac : 23;
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uint32_t expo : 8;
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uint32_t sign : 1;
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} data;
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};
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if (x < 0)
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return 1.0f / fast_exp2f(-x);
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union _float f = {.f = 1.0f};
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f.data.expo = (int)x + 127;
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return _fast_exp2f(x - (int)x) * f.f;
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}
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float fast_expf(float x)
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{
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extern float __ieee754_expf(float x);
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return __ieee754_expf(x);
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}
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float fast_powf(float base, float expo)
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{
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extern float __ieee754_powf(float base, float expo);
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return __ieee754_powf(base, expo);
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}
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