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    <p>Most implementations I know use a 1D array with wrappers either via MACROS or methods to access the 2D data. I myself can't say which is faster and I can hardly see a case where this would really matter.</p> <p>However this being said I would still recommend using 1D arrays for the following reasons:</p> <ol> <li>easier to allocate and release dynamically (If you want to allocate your data dynamically and maintain the matrix[i][j] pattern then you are allocating an array of arrays - slower to allocate more bug prone, you have to release each array separately)</li> <li>if you allocate dynamically and have to copy the data to a 3d party library say OpenGL or OpenCV you are into some trouble since they need the data to be contiguous.</li> <li>It will be easier to store and read the matrix from files or other persistent storage.</li> <li>even if you don't allocate dynamically you will have to do all sorts of ugly castings to handle the transfer of memory to 3d party libraries.</li> <li>it's super easy to create a structure with methods to have efficient 2d access to your data without multiplications or unclear indexing. Or for that matter use MACROS to encapsulate the ugly multiplications for you.</li> <li>You could even create a structure to look like the next sample and maintain the same benefits of a 1d array with the readability of a 2d array:</li> </ol> <pre><code> template&lt;typename T&gt; struct Matrix4x4 { struct index { int row, col; index(int r = 0, int c = 0) : row(r), col(c){} index(index const & cp) : row(cp.row), col(cp.col) { } //Assignment ommited for brevity }; /* Constructors, Assignments etc. ommited for brevity */ T m00, m01, m02, m03; T m10, m11, m12, m13; T m20, m21, m22, m23; T m30, m31, m32, m33; T * toArray() const { return &m00; } T * toArray() { return &m00; } T * row(int r) { return (&m00) + r*4; } T * row(int r) const { return (&m00) + r*4; } T & operator()(int r, int c) { return *row(r)[c]; } T const & operator()(int r, int c) const { return *row(r)[c]; } T & operator[](index const & idx) { return row(idx.row)[idx.col]; } T const & operator[](index const & idx) const { return row(idx.row)[idx.col]; } }; </code></pre> <p>In your code you can do:</p> <pre><code>typedef Matrix4x4&lt;double&gt; Matrix4x4d; Matrix4x4d mat; /* You can do any of the following */ mat.m23 = 6.0; mat(2,3) = 6.0; mat[Matrix4x4d::index(2,3)] = 6.0; mat.row(2)[3] = 6.0; mat.toArray()[2*4 + 3] = 6.0; #define M(m,r,c) (*((&amp;m.m00) + r*4 + c)) M(mat,2,3) = 6.0; </code></pre> <p>I myself implemented several matrix libraries over the years and always opted for the 1d solution.</p>
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