| // Copyright 2019 The SwiftShader Authors. All Rights Reserved. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| #include "System/Half.hpp" |
| |
| #include <gtest/gtest.h> |
| #include <gmock/gmock.h> |
| |
| #include <cstdlib> |
| |
| using namespace sw; |
| |
| // Clamps to the [0, hi] range. NaN input produces 0, hi must be non-NaN. |
| float clamp0hi(float x, float hi) |
| { |
| // If x=NaN, x > 0 will compare false and we return 0. |
| if(!(x > 0)) |
| { |
| return 0; |
| } |
| |
| // x is non-NaN at this point, so std::min() is safe for non-NaN hi. |
| return std::min(x, hi); |
| } |
| |
| unsigned int RGB9E5_reference(float r, float g, float b) |
| { |
| // Vulkan 1.1.117 section 15.2.1 RGB to Shared Exponent Conversion |
| |
| // B is the exponent bias (15) |
| constexpr int g_sharedexp_bias = 15; |
| |
| // N is the number of mantissa bits per component (9) |
| constexpr int g_sharedexp_mantissabits = 9; |
| |
| // Emax is the maximum allowed biased exponent value (31) |
| constexpr int g_sharedexp_maxexponent = 31; |
| |
| constexpr float g_sharedexp_max = |
| ((static_cast<float>(1 << g_sharedexp_mantissabits) - 1) / |
| static_cast<float>(1 << g_sharedexp_mantissabits)) * |
| static_cast<float>(1 << (g_sharedexp_maxexponent - g_sharedexp_bias)); |
| |
| const float red_c = clamp0hi(r, g_sharedexp_max); |
| const float green_c = clamp0hi(g, g_sharedexp_max); |
| const float blue_c = clamp0hi(b, g_sharedexp_max); |
| |
| const float max_c = fmax(fmax(red_c, green_c), blue_c); |
| const float exp_p = fmax(-g_sharedexp_bias - 1, floor(log2(max_c))) + 1 + g_sharedexp_bias; |
| const int max_s = static_cast<int>(floor((max_c / exp2(exp_p - g_sharedexp_bias - g_sharedexp_mantissabits)) + 0.5f)); |
| const int exp_s = static_cast<int>((max_s < exp2(g_sharedexp_mantissabits)) ? exp_p : exp_p + 1); |
| |
| unsigned int R = static_cast<unsigned int>(floor((red_c / exp2(exp_s - g_sharedexp_bias - g_sharedexp_mantissabits)) + 0.5f)); |
| unsigned int G = static_cast<unsigned int>(floor((green_c / exp2(exp_s - g_sharedexp_bias - g_sharedexp_mantissabits)) + 0.5f)); |
| unsigned int B = static_cast<unsigned int>(floor((blue_c / exp2(exp_s - g_sharedexp_bias - g_sharedexp_mantissabits)) + 0.5f)); |
| unsigned int E = exp_s; |
| |
| return (E << 27) | (B << 18) | (G << 9) | R; |
| } |
| |
| TEST(MathTest, SharedExponentSparse) |
| { |
| for(uint64_t i = 0; i < 0x0000000100000000; i += 0x400) |
| { |
| float f = bit_cast<float>(i); |
| |
| unsigned int ref = RGB9E5_reference(f, 0.0f, 0.0f); |
| unsigned int val = RGB9E5(f, 0.0f, 0.0f); |
| |
| EXPECT_EQ(ref, val); |
| } |
| } |
| |
| TEST(MathTest, SharedExponentRandom) |
| { |
| srand(0); |
| |
| unsigned int x = 0; |
| unsigned int y = 0; |
| unsigned int z = 0; |
| |
| for(int i = 0; i < 10000000; i++) |
| { |
| float r = bit_cast<float>(x); |
| float g = bit_cast<float>(y); |
| float b = bit_cast<float>(z); |
| |
| unsigned int ref = RGB9E5_reference(r, g, b); |
| unsigned int val = RGB9E5(r, g, b); |
| |
| EXPECT_EQ(ref, val); |
| |
| x += rand(); |
| y += rand(); |
| z += rand(); |
| } |
| } |
| |
| TEST(MathTest, SharedExponentExhaustive) |
| { |
| for(uint64_t i = 0; i < 0x0000000100000000; i += 1) |
| { |
| float f = bit_cast<float>(i); |
| |
| unsigned int ref = RGB9E5_reference(f, 0.0f, 0.0f); |
| unsigned int val = RGB9E5(f, 0.0f, 0.0f); |
| |
| EXPECT_EQ(ref, val); |
| } |
| } |