Modified source engine (2017) developed by valve and leaked in 2020. Not for commercial purporses
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//========= Copyright Valve Corporation, All rights reserved. ============//
//
// Purpose:
//
// A class allowing storage of a sparse NxN matirx as an array of sparse rows
//===========================================================================//
#ifndef SPARSEMATRIX_H
#define SPARSEMATRIX_H
#include "tier1/utlvector.h"
/// CSparseMatrix is a matrix which compresses each row individually, not storing the zeros. NOte,
/// that while you can randomly set any element in a CSparseMatrix, you really want to do it top to
/// bottom or you will have bad perf as data is moved around to insert new elements.
class CSparseMatrix
{
public:
struct NonZeroValueDescriptor_t
{
int m_nColumnNumber;
float m_flValue;
};
struct RowDescriptor_t
{
int m_nNonZeroCount; // number of non-zero elements in the row
int m_nDataIndex; // index of NonZeroValueDescriptor_t for the first non-zero value
};
int m_nNumRows;
int m_nNumCols;
CUtlVector<RowDescriptor_t> m_rowDescriptors;
CUtlVector<NonZeroValueDescriptor_t> m_entries;
int m_nHighestRowAppendedTo;
void AdjustAllRowIndicesAfter( int nStartRow, int nDelta );
public:
FORCEINLINE float Element( int nRow, int nCol ) const;
void SetElement( int nRow, int nCol, float flValue );
void SetDimensions( int nNumRows, int nNumCols );
void AppendElement( int nRow, int nCol, float flValue );
void FinishedAppending( void );
FORCEINLINE int Height( void ) const { return m_nNumRows; }
FORCEINLINE int Width( void ) const { return m_nNumCols; }
};
FORCEINLINE float CSparseMatrix::Element( int nRow, int nCol ) const
{
Assert( nCol < m_nNumCols );
int nCount = m_rowDescriptors[nRow].m_nNonZeroCount;
if ( nCount )
{
NonZeroValueDescriptor_t const *pValue = &(m_entries[m_rowDescriptors[nRow].m_nDataIndex]);
do
{
int nIdx = pValue->m_nColumnNumber;
if ( nIdx == nCol )
{
return pValue->m_flValue;
}
if ( nIdx > nCol )
{
break;
}
pValue++;
} while( --nCount );
}
return 0;
}
// type-specific overrides of matrixmath template for special case sparse routines
namespace MatrixMath
{
/// sparse * dense matrix x matrix multiplication
template<class BTYPE, class OUTTYPE>
void MatrixMultiply( CSparseMatrix const &matA, BTYPE const &matB, OUTTYPE *pMatrixOut )
{
Assert( matA.Width() == matB.Height() );
pMatrixOut->SetDimensions( matA.Height(), matB.Width() );
for( int i = 0; i < matA.Height(); i++ )
{
for( int j = 0; j < matB.Width(); j++ )
{
// compute inner product efficiently because of sparsity
int nCnt = matA.m_rowDescriptors[i].m_nNonZeroCount;
int nDataIdx = matA.m_rowDescriptors[i].m_nDataIndex;
float flDot = 0.0;
for( int nIdx = 0; nIdx < nCnt; nIdx++ )
{
float flAValue = matA.m_entries[nIdx + nDataIdx].m_flValue;
int nCol = matA.m_entries[nIdx + nDataIdx].m_nColumnNumber;
flDot += flAValue * matB.Element( nCol, j );
}
pMatrixOut->SetElement( i, j, flDot );
}
}
}
FORCEINLINE void AppendElement( CSparseMatrix &matrix, int nRow, int nCol, float flValue )
{
matrix.AppendElement( nRow, nCol, flValue ); // default implementation
}
FORCEINLINE void FinishedAppending( CSparseMatrix &matrix )
{
matrix.FinishedAppending();
}
};
#endif // SPARSEMATRIX_H