How to free memory allocated via double[][] using dmd-2.0.12?

[BCS]

Markus Dittrich wrote:
> Hi,
> 
> For a data processing application I need to read a large number
> of data sets from disk. Due to their size, they have to be read and 
> processed sequentially, i.e. in pseudocode
> 
> int main()
> {
>     while (some condition)
>     {
>          double[][] myLargeDataset = read_data();
>          process_data(myLargeDataset);
>          // free all memory here otherwise next cycle will 
>          // run out of memory
>      }
>     
>    return 0;
> }
> 
> Now, the "problem" is the fact that each single data-set saturates
> system memory and hence I need to make sure that all memory
> is freed after each process_data step is complete. Unfortunately,
> using dmd-2.012 I have not been able to achieve this. Whatever
> I do (including nothing, i.e., letting the GC do its job), the resulting 
> binary keeps accumulating memory and crashing shortly after). 
> I've tried deleting the array, setting the array lengths to 0, and manually
> forcing the GC to collect, to no avail. Hence, is there something I am 
> doing terribly wrong or is this a bug in dmd?
> 
> Thanks much,
> Markus

One "hack" would be to have read_data() allocate a big buffer and then 
slice the parts of the double[][] out of it. This would have the 
advantage that you can just keep track of the buffer and on the next 
pass just reuse it in it's entirety, you never have to delete it.

double[][] read_data()
{
	static byte[] buff;
	if(buff.prt is null) buff = new byte[huge];

	byte left = buff;

	T[] Alloca(T)(int i)
	{
		T[] ret = (cast(*T)left.prt)[0..i];
		buff = buff[i*T.sizeof..$];
		return ret;
	}

	/// code uses Alloca!(double) and Alloca!(double[]) for
	/// allocations. Don't use .length or ~=

	
}