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A quick test of small Eigen vector classes. Tested on visual Studio 15.9.2, release 64 bit.
#include "stdafx.h"
// A quick test of small Eigen vector classes. Tested on visual Studio 15.9.2, release 64 bit.
#define EIGEN_VECTORIZE_SSE
#define EIGEN_VECTORIZE_SSE2
#define EIGEN_VECTORIZE_SSE3
#define EIGEN_VECTORIZE_SSE4_1
#include "Eigen/Dense"
#include <d3d11.h>
#include <DirectXMath.h>
using Eigen::Vector3f;
using Eigen::Vector4f;
using Float3 = DirectX::XMFLOAT3;
using Float4 = DirectX::XMFLOAT4;
__forceinline Vector3f load( const Float3& v )
{
return Vector3f{ v.x, v.y, v.z };
}
__forceinline Vector4f load( const Float4& v )
{
return Vector4f{ v.x, v.y, v.z, v.w };
}
float __declspec( noinline, dllexport ) testVectorMath3( const Float3& fa, const Float3& fb )
{
const Vector3f a = load( fa );
const Vector3f b = load( fb );
__debugbreak();
// This code is not vectorized. Compiles into stuff like mulss, addss, subss, even with /fp:fast, produces 26 instructions.
// Either there's problem in Eigen or VC++, or it's just not complex enough, hard to tell.
const Vector3f c = a.array() * b.array();
const Vector3f d = a + b + c;
const Vector3f e = c.array() * d.array();
return d.dot( e );
}
float __declspec( noinline, dllexport ) testVectorMath4( const Float4& fa, const Float4& fb )
{
const Vector4f a = load( fa );
const Vector4f b = load( fb );
__debugbreak();
// This code is vectorized fine, compiles into stuff like mulps, addps, shufps, only emits 14 instructions.
const Vector4f c = a.array() * b.array();
const Vector4f d = a + b + c;
const Vector4f e = c.array() * d.array();
return d.dot( e );
}
void test3()
{
const Float3 a{ 1, 2, 3 }, b{ 4, 5, 6 };
const float res = testVectorMath3( a, b );
printf( "result 3: %f\n", res );
}
void test4()
{
const Float4 a{ 1, 2, 3, 4 }, b{ 5, 6, 7, 8 };
const float res = testVectorMath4( a, b );
printf( "result 4: %f\n", res );
}
int main()
{
test3();
test4();
return 0;
}
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