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POCorrect way of dynamic memory allocation for high-dimensional arrays in C++?
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copied!<p>I was wondering what is the easiest and of course most accurate way for dynamic memory allocation for a 4-D array in C++. What I already know is the following:</p> <pre><code>double**** A; A = new double***[s1]; for (i = 0; i < s1; i++) { A[i] = new double**[s2]; for (j = 0; j < s2; j++) { A[i][j] = new double*[s3]; for (k = 0; k < s3; k++) { A[i][j][k] = new double[s4]; } } } </code></pre> <p>to declare <code>A</code> as a 4-D array of dimensions <code>s1</code>x<code>s2</code>x<code>s3</code>x<code>s4</code>. </p> <p>However, the above is not safe. In the sense that if one of the <code>new</code>s fail to allocate the memory the loops continue without noticing this. </p> <p>To make the above a bit safer, we can enclose it in a <code>try</code>/<code>catch</code> block so that the code does not continue after a <code>bad_alloc</code> has been thrown by <code>new</code> and the code will not try to access some non-existent memory elements and the program can halt at this point.</p> <p>This is OK with the exception that the memory that has already been allocated will not be released before the program finishes. Theoretically with the values of <code>i</code>, <code>j</code>, and <code>k</code> we must be able to precisely say which memory elements are already allocated and release them. But I cannot think of a straightforward way of doing it.</p> <p>For a 2-D case I would do something like this:</p> <pre><code>double** A; try { A = new double*[s1]; } catch(bad_alloc& ba) { delete[] A; throw ba; // or end the program } try { for (i = 0; i < s1; i++) A[i] = new double[s2]; } catch(bad_alloc& ba) { while(--i) { delete[] A[i]; } delete[] A; throw ba; // or end the prog. } </code></pre> <p>The above could be generalized to higher dimensional arrays but I guess it would be very ugly! So I wonder if there is a better way for doing that?</p> <hr> <p>I guess I should also mention that in my case <code>A[i][j][k]</code> is a vector with very few non-zero elements. Hence, I only take <code>s3</code> to be as big as the number of non-zero elements (and then take care of mapping indices and ... later). <code>s3</code>, however, depends on <code>j</code>. That's why using the traditional memory allocation is easier than higher-level APIs like <code>vector</code></p>

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