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AK: Add AK::SIMD::exp_approximate

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This approximation tries to generate values within 0.1% of their actual
expected value. Microbenchmarks indicate that this iterative SIMD
version can be up to 60x faster than `AK::SIMD::exp`.
This commit is contained in:
Jelle Raaijmakers 2023-02-17 17:06:03 +01:00 committed by Andreas Kling
parent 3275d659bf
commit f4342c9118
Notes: sideshowbarker 2024-07-17 17:06:59 +09:00 
Author: https://github.com/gmta
Commit: https://github.com/SerenityOS/serenity/commit/f4342c9118
Pull-request: https://github.com/SerenityOS/serenity/pull/17504
3 changed files with 43 additions and 0 deletions
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9
AK/SIMDMath.h
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@ -66,6 +66,15 @@ ALWAYS_INLINE static f32x4 exp(f32x4 v)
};
}
ALWAYS_INLINE static f32x4 exp_approximate(f32x4 v)
{
static constexpr int number_of_iterations = 10;
auto result = 1.f + v / (1 << number_of_iterations);
for (int i = 0; i < number_of_iterations; ++i)
result *= result;
return result;
}
ALWAYS_INLINE static f32x4 sqrt(f32x4 v)
{
#if ARCH(x86_64)

1
Tests/AK/CMakeLists.txt
View file

@ -61,6 +61,7 @@ set(AK_TEST_SOURCES
TestQuickSort.cpp
TestRedBlackTree.cpp
TestRefPtr.cpp
TestSIMD.cpp
TestSinglyLinkedList.cpp
TestSourceGenerator.cpp
TestSourceLocation.cpp

33
Tests/AK/TestSIMD.cpp Normal file
View file

@ -0,0 +1,33 @@
/*
* Copyright (c) 2023, Jelle Raaijmakers <jelle@gmta.nl>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibTest/TestCase.h>
#include <AK/SIMD.h>
#include <AK/SIMDMath.h>
TEST_CASE(exp)
{
AK::SIMD::f32x4 v = { .2f, .4f, .6f, .8f };
auto result = AK::SIMD::exp(v);
EXPECT_APPROXIMATE(result[0], 1.22140276f);
EXPECT_APPROXIMATE(result[1], 1.49182470f);
EXPECT_APPROXIMATE(result[2], 1.82211880f);
EXPECT_APPROXIMATE(result[3], 2.22554093f);
}
TEST_CASE(exp_approximate)
{
AK::SIMD::f32x4 v = { .2f, .4f, .6f, .8f };
auto result = AK::SIMD::exp_approximate(v);
constexpr float accuracy = .001f;
EXPECT(fabsf(result[0] - 1.22140276f) <= accuracy);
EXPECT(fabsf(result[1] - 1.49182470f) <= accuracy);
EXPECT(fabsf(result[2] - 1.82211880f) <= accuracy);
EXPECT(fabsf(result[3] - 2.22554093f) <= accuracy);
}