mirror of
https://github.com/yuzu-emu/FasTC
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93 lines
3 KiB
C++
93 lines
3 KiB
C++
/*******************************************************************************
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* Copyright (c) 2012 Pavel Krajcevski
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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*
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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*
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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*
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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*
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* 3. This notice may not be removed or altered from any source
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* distribution.
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*
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******************************************************************************/
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#ifndef BASE_INCLUDE_MATRIXSQUARE_H_
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#define BASE_INCLUDE_MATRIXSQUARE_H_
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#include "MatrixBase.h"
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namespace FasTC {
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template <typename T, const int N>
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class MatrixSquare : public MatrixBase<T, N, N> {
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public:
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// Constructors
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MatrixSquare() { }
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MatrixSquare(const MatrixSquare<T, N> &other)
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: MatrixBase<T, N, N>(other) { }
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MatrixSquare(const MatrixBase<T, N, N> &other)
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: MatrixBase<T, N, N>(other) { }
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// Does power iteration to determine the principal eigenvector and eigenvalue.
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// Returns them in eigVec and eigVal after kMaxNumIterations
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int PowerMethod(VectorBase<T, N> &eigVec, T *eigVal = NULL,
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const int kMaxNumIterations = 200) {
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int numIterations = 0;
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// !SPEED! Find eigenvectors by using the power method. This is good because the
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// matrix is only 4x4, which allows us to use SIMD...
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VectorBase<T, N> b;
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for(int i = 0; i < N; i++)
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b[i] = T(1.0);
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b /= b.Length();
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bool fixed = false;
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numIterations = 0;
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while(!fixed && ++numIterations < kMaxNumIterations) {
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VectorBase<T, N> newB = (*this).operator*(b);
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// !HACK! If the principal eigenvector of the covariance matrix
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// converges to zero, that means that the points lie equally
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// spaced on a sphere in this space. In this (extremely rare)
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// situation, just choose a point and use it as the principal
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// direction.
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const float newBlen = newB.Length();
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if(newBlen < 1e-10) {
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eigVec = b;
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if(eigVal) *eigVal = 0.0;
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return numIterations;
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}
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T len = newB.Length();
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newB /= len;
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if(eigVal)
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*eigVal = len;
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if(fabs(1.0f - (b.Dot(newB))) < 1e-5)
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fixed = true;
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b = newB;
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}
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eigVec = b;
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return numIterations;
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}
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};
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};
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#endif // BASE_INCLUDE_MATRIXSQUARE_H_
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