修改的malloc战略二维数组，这样成功的malloc [英] Modify malloc strategy for 2D Array so malloc succeeds

问题描述

我们最近收到一份报告，我们的应用程序有时可能不运行。我找到了问题所在code这样：

We recently received a report that our application will occasionally fail to run. I tracked down the problem code to this:

struct ARRAY2D
{
   long[] col;
}

int numRows = 800000;
int numCols = 300;
array = (ARRAY2D*) malloc(numRows * numCols * sizeof(long))

800兆的这种分配，如果用户不具有一个足够大的空闲块可能会失败。什么是改变我如何分配内存的最好方法？

This allocation of 800 Mb can fail if the user doesn't have a large enough free block. What is the best way to change how I allocate the memory?

请记住，我有一个访问该对象像这样大量的code的：数组[行] .COL [colNum]，所以我需要的东西，需要的未成年人或主要查找和放大器;更换阵列访问code的的编辑。

Keep in mind that I have a large amount of code that accesses this object like this: array[row].col[colNum], so I need something that requires minor or primarily find & replace editing of the array access code.

推荐答案

您可以单独分配的内存较小的块，而不是一个巨大的块。

You can allocate smaller chunks of memory separately, instead of one huge block.

long** array = NULL;  
array = (long**) malloc(numCols * sizeof(long*));  
for (int i = 0; i < numCols; i++)  
   array[i] = (long*)  malloc(numRows * sizeof(long));

一般来说，内存分配可能失败，每次分配。然而，假设统计，由于内存碎片，分配的内存一个大块更高的机会比分配更小的块的N多更容易发生故障。
虽然，也高于该解决方案可能会导致问题，因为它是一个有点像双刃的剑，因为这可能导致进一步的内存碎片。

Generally, memory allocation may fail, every allocation. However, let's say statistically, due to memory fragmentation, allocating a single large block of memory has higher chance to fail more often than allocating N number of smaller blocks. Although, also the solution above may cause problems as it is a bit like a double-bladed sword because it may lead to further memory fragmentation.

在换句话说，没有一般完美的答案和解决方案，取决于系统和应用程序的细节。

In other words, there is no generally perfect answer and solution depends on details of a system and application.

由于从评论，似乎C ++库是一种可能性，则解决方案基于的std ::矢量（即<一href=\"http://stackoverflow.com/questions/293988/generic-vector-of-vectors-in-c/2211411#2211411\">generic在C ++中向量的矢量）或使用 Boost.MultiArray的

As from the comments it seems C++ library is a possibility, then solution based on std::vector (i.e. generic vector of vectors in C++) or using Boost.MultiArray

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