blob: dbedd9ee7fa3320bc9b03e733f3842feaa9c2a1d [file] [log] [blame]
// 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);
}
}