Need Help

**Shafiul** · 10-27-2019

Code:

    regarding header : memorytest.h
   /*#ifndef MEMORYTEST_H
   #define MEMORYTEST_H
    #include <stdlib.h>
    template <class type1, class type2>
    void allocateData1DbyMalloc(type1** data1D, type2 nRow) {
	int size = (char*) &(*data1D)[1] - (char*) & (*data1D)[0];
	*data1D = (type1*)malloc(nRow * size); // sizeof(type1));
     }


     template <class type1>
     void deAllocateData1DbyFree(type1** data1D) {
	free(*data1D);
     }


       template <class type1, class type2>
       void allocateData2DbyMalloc(type1*** data2D, type2 nRow, type2 nColumn) {
	int size = (char*) & (*data2D)[1] - (char*) & (*data2D)[0];
	*data2D = (type1 * *)malloc(size * nRow); // sizeof(type1*)
	if (*data2D) {
		size = (char*) & (**data2D)[1] - (char*) & (**data2D)[0];
	for (int i = 0; i < nRow; i++) {
				(*data2D)[i] = (type1*)malloc(size * nColumn); // sizeof(type1)
		}
	}
      }


      template <class type1, class type2>
      void destroyMatrix2DbyFree(type1*** data2D, type2 numberOfRow) {
	for (int row = 0; row < numberOfRow - 1; row++)
		free((*data2D)[row]);
	free(*data2D);
      }
      #endif

**Shafiul** · 10-27-2019

you can try this header. hope, it should work

**laserlight** · 10-27-2019

It doesn't work for certain class types. I already explained why.

Why don't you want to use sizeof?

You explained why you don't want to use containers, but your explanation goes against best practice which is to default to containers, then measure and if containers turn out to be unacceptable, implement your own. Why don't you want to program in best practice C++?

You explained your thinking behind using malloc so that you can replace malloc with something else. I informed you that the normal approach in C++ is to define a custom allocator for that "something else". Why don't you want to do this?

**laserlight** · 10-27-2019

Oh sorry, I missed this because it was at the bottom of the previous page.

Originally Posted by Shafiul

Hi Laserlight, well, i don't know the answer of "I'm talking about correctly invoking constructors" because I don't get the question honestly. Can you explain your question a bit please if possible. Then i will try to do my best to answer it.

Are you familiar with classes and constructors in C++?

Originally Posted by Shafiul

Well, the idea is GPU system need a memory mapping between cudamalloc and malloc to transfer the data from CPU to GPU. Based on the memory mapping, sometimes I need to call realloc() to optimise the memory mapping between CPU and GPU.

I'm not familiar with what you want to do, but as far as I know, the allocator system in C++ was designed to be flexible enough to handle unusual allocation requirements without sacrificing efficiency. Have you looked into implementing a custom allocator?

The thing is, from post #1 it looked like you decided to write something that is entirely in C other than the use of function templates for generics. The problematic thing is that your code does resource allocation, and in a C++ context where there's the danger of exceptions being propagated around, failing to do things the "C++ way" means that your code might not be exception safe if you aren't exceptionally careful. So, you should either make use of C++ facilities for resource management, or rewrite your code in C even if that means pain from being unable to use templates.

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