halfsquarematrix.h

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/*
* Copyright 2016 Autodesk, Inc. All rights reserved.
* Use of this software is subject to the terms of the Autodesk license agreement and any attachments or Appendices thereto provided at the time of installation or download,
* or which otherwise accompanies this software in either electronic or hard copy form, or which is signed by you and accepted by Autodesk.
*/

#pragma once


#include "gwnavruntime/base/types.h"
#include "gwnavruntime/kernel/SF_Types.h"

namespace Kaim
{

template <class T>
class HalfSquareMatrix
{
public:
    HalfSquareMatrix()
        : m_buffer(nullptr)
        , m_bufferSize(0)
        , m_count(0)
    {}

    HalfSquareMatrix(T* buffer, KyUInt32 bufferSize, KyUInt32 count)
        : m_buffer(buffer)
        , m_bufferSize(bufferSize)
        , m_count(count)
    {}

    T* GetValue(KyUInt32 rowIdx, KyUInt32 columnIdx) const
    {
        if (rowIdx < columnIdx)
        {
            KyUInt32 index = GetIndexInHalfMatrix(rowIdx, columnIdx);
            return &m_buffer[index];
        }
        else if (rowIdx > columnIdx)
            return GetValue(columnIdx, rowIdx); // invert column and row
        else // if (rowIdx == columnIdx)
            return nullptr;
    }

public: //internal

    // rowIdx must be strictly smaller than columnIdx
    KyUInt32 GetIndexInHalfMatrix(KyUInt32 rowIdx, KyUInt32 columnIdx) const
    {
        KY_ASSERT(rowIdx < columnIdx);
        KyUInt32 count = GetCount();
        // index = (n*i+j) - (((i+1)^2)-(((i+1)^2)-(i+1))/2), where i is row, j is column, n is number of abstractGraphNodeCount
        KyUInt32 fullMatrixIdx = count * rowIdx + columnIdx; // n*i+j
        KyUInt32 rowSizedMatrixLength = rowIdx+1; // i+1
        KyUInt32 rowSizedMatrixSize = rowSizedMatrixLength*rowSizedMatrixLength; // (i+1)*(i+1)
        KyUInt32 rowSizedHalfMatrixSize = (rowSizedMatrixSize - rowSizedMatrixLength)/2; // (((i+1)*(i+1))-(i+1))/2
        KyUInt32 elementToRemoveFromFullMatrix = rowSizedMatrixSize - rowSizedHalfMatrixSize; // (((i+1)*(i+1))-(((i+1)*(i+1))-(i+1))/2)
        KyUInt32 index = fullMatrixIdx - elementToRemoveFromFullMatrix; // (n*i+j) - (((i+1)*(i+1))-(((i+1)*(i+1))-(i+1))/2)
        return index;
    }

    KyUInt32 GetCount() const
    {
        return m_count;
        //      if (m_bufferSize == 0)
        //          return 0;
        //
        //      // quadratic formula : (1)*n*n + (-1)*n + (-size*2) = 0
        //      // discriminant : 1 - (4 * (-size*2)) //< always positive so there are 2 solutions
        //      // n = (1 +/- sqrt(1-4*(-size*2)))/2*1 //< pickup only the positive solution
        //      KyUInt32 res = (KyUInt32) (1.f + Sqrtf(1.f+8.f*((KyFloat32)m_bufferSize)));
        //      return (res >> 1);
    }

    KyUInt32 ComputeBufferSize(KyUInt32 count) const
    {
        return ((count*count)-count) / 2;
    }

public:
    // Here's how index of m_buffer are constructed,
    // values given into the array are the corresponding index in m_buffer
    //
    // +-- Idx, m_count by m_count -----+
    // |                                |
    // V | 0 1 2 3 4   <----------------+
    // --+------------
    // 0 | # 0 1 2 3 T
    // 1 | x # 4 5 6 |
    // 2 | x x # 7 8 |
    // 3 | x x x # 9 L___ indices in m_buffer
    // 4 | x x x x #
    //
    // size of this array is (((n*n)-n) / 2) where n is m_count
    //
    T* m_buffer;
    KyUInt32 m_bufferSize;
    KyUInt32 m_count;
};

}