I would like to know if a function/subroutine/system call exists to output the amount of physical memory used by my Fortran code.
I'm currently facing some memory leaks and I would like to understand exactly where they are coming from.
I am using ifort compiler on windows (Intel Inspector is not an option for the moment).
Thank you for proposing this tool. It seems very interesting.
However, I'm looking for something to be integrated directly in my code (such as a function call). So that I can check the amount of memory used during the execution.
Not the answer you expect, but maybe nevertheless helpful. It is an exert from a book Modern Fortran explained by Michael Metcalf, John Reid, and Malcolm Cohen, Oxford University Press, page 104:
Note also that the standard does not specify whether the processor recovers storage allocated through a pointer but no longer accessible through this or any other pointer. This failure to recover storage is known as memory leakage. It might be important where, for example, a pointer function is referenced within an expression - the programmer cannot rely on the compiler to arrange for deallocation. To ensure that there is no memory leakage, it is necessary to use such functions only on the right-hand side of pointer assignments or as pointer component values in structure constructors, and to deallocate the pointer when it is no longer needed.
If you happen to run Fortran 2003, then you have at your disposal a function
size (array [,dim] [,kind])
Memory leak mostly occurs when you are using class/type. The compiler destroy whatever declared in the static memory (not in the heap). So if you are using pointers or allocatable arrays within the type/class definition, make sure you deallocate them in the final function that you must provide in the code. You may find the point of the memory leak by turning each of the pointer arrays into a static array (one-by-one) and check if the memory leakage solved.
There are some circumstances (i.e. copying a class in actual argument to the dummy argument with intent (IN) attributes ) that compiler copies the content of type in the actual argument to a temporarily allocated type in the dummy argument. You should take care of these situation, since the compiler does not tell you that it is copying the content and then destroying the temporarily allocated type. By providing copy and assignment constructors, you can manage these operations.
Thank you Hamidreza ! Your comment helped me to find some of the leaks.
I'm still investigating for a function (or equivalent) to be called from the fortran code to do some automatic tests.
I have never had this problems. You may can use some memory/process profilers to do so.
I am currently programming in CUDA and NVIDIA provided such profilers. Sorry that I can not help you in this regard. But still there are some ways to solve this problem without a profiler. But it needs you to show a prototype of your code here to see how to fix it. I also recommend you to consult your problem with http://stackoverflow.com
I sometimes consult the members of this website and find solutions for my problems.
As far as I know there is no function directly available in Fortran. The easiest way to do this is to write a function in C which uses according functions from the operating system and computes the information that you need. Then, you call this C function from within Fortran. For this you need an interface written in Fortran which will fit the interface of the C function (the Fortran keyword BIND(C) is very helpful for this).
What Hamidreza mentioned about unintentional copies being made there is a way to figure out where this occurs. The compiler will not tell you directly. But, when you compile with ifort using the flag '-check all' you will get runtime warnings when copies occur. You should be aware, though, that this compiler flag turns off all optimizations. Because of this your software will run up to 10 or 20 times slower.
I would recommend to use Intel profiler (actually there several separated tools which help to solve different problems with code), it has many features and can detect virtually any problem. Unfortunately it's not free, but you can download trial version (it works for 30days without any limitations) from intel website.
I also, wanted to find a command to see the memory usage (at least the available mem), so I find out I can run Unix command from Fortran, by
CALL system(command)
i.e. CALL system('free -m')
So, it may help.
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