use visibility=export>
This class reports on the dynamic ("heap") memory used by this process, and it can attempt to release some of that memory back to the operating system. The class reports on allocated memory, which is memory that the process has actually requested, typically via new, but also via malloc. The number might be somewhat larger than actually requested by the programmer to account for overhead and alignment considerations. The class also reports assigned memory, which is the total memory that the process has been given, not all of which has been allocated by the programmer. Typically this results from memory which has been deleted by the programmer, but has not been released to the OS on the assumption that it might be needed again. (Getting and releasing memory to the OS can be expensive).
At present, the values for allocated and assigned memory are obtained via the mallinfo() call, usually defined in malloc.h. This call seems to be adequately portable for Unix. Another alternative would be to replace global operators new and delete for systems that do not have mallinfo().
The member function releaseMemory() on some system will attempt to return assigned but unallocated memory to the OS. If the compilation system cannot automatically determine how to do this (at present it only recognizes Linux systems), you can you this function by setting the preprocessor symbol AIPS_RELEASEMEM to a C++ statement which will release memory to the OS. For example, if you are using GNU malloc you could set it to malloc_trim(0). Note that releaseMemory() might be a no-op on many systems, and that calling it might be expensive so it should not be called in tight-loops.
Note that this class does not use any AIPS++ facilities and does not cause any AIPS++ code to be linked in to your executable.
if (Memory::assignedMemoryInBytes() - Memory::allocatedMemoryInBytes() > 1024*1024) { Memory::releaseMemory(); // Attempt to release if more than 1M "wasted" }
setMemoryOptions and setMemoryOption are typically front ends for mallopt which lets the user control some memory allocation parameters. setMemoryOptions is intended to be called only once at the start of a program while setMemoryOption could be called where desired (but see mallopt man page for possible side effects). Note: these two functions were added to address in a general way a memory fragmentation problem encountered on by the MIPSpro C++ compiler on the SGI.