memory allocation issues

[tguzella]

hi there, i am writing a c++ program to make statistical analysis, which demands quite some memory (i'm using new to allocate an array and filling it with values)... whenever i need to allocate close to 200 mb the program and the computer gets really slow, taking forever just to allocate the memory... this happen when compilling on vc 6 and vc 7. when using dev c++ (mingw), the program just crashes while trying to allocate the memory... i am pretty much sure thats nothing to deal with memory leaks (all memory allocate is freed in the end), bad memory chips (i tested them using memtest) or insufficient memory (this pc runs with 2 gb of ram memory)... any suggestions on how to solve this??????

[David Crow]

tguzella wrote: whenever i need to allocate close to 200 mb the program and the computer gets really slow, taking forever just to allocate the memory This sounds reasonable. Allocating that much requires a good deal of work by the memory manager, including lots of virtual disk activity.

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Five birds are sitting on a fence. Three of them decide to fly off. How many are left?

[ZoogieZork]

Is this memory being allocated in lots of tiny chunks or as one big array? In either case, the virtual memory manager will be working overtime to figure out how to arrange blocks and track them. If you have a whole bunch of tiny memory blocks, you might consider allocating a large pool of memory at the start of the day and writing your own allocator tuned to your requirements. - Mike

[Neville Franks]

Well allocating 200M sounds like a really bad idea, and is going to take quite some time. I'd be trying to find better algorithm or implementation of your algorithm that doesn't need such vast amounts of memory, or acquires it only as needed. There are also small memory block allocators around which will considerably improve performance if you are allocating lots of small blocks. Neville Franks, Author of ED for Windows. Free Trial at www.getsoft.com

[John M Drescher]

Well I would say for me 200MB is not a lot of memory. My program allocates almost 2GB which is the maximum allowed by the version of windows I am using. I do my allocations using VirtualAlloc(). I have almost 2GB of free memory and my allocations are instantaneous (take a few microseconds if you are counting). The first thing I would say is to check task manager to see if you have any free ram before you do the allocation. Are you using any third party memory products?? The ones that claim to give you more memory?? If so disable them and see what happens... John

[tguzella]

actually i am allocating this memory for 3 arrays... i am not using any third party allocation program... If this might be the problem, could anyone suggest me one to use (a freeware if possible :)...)??? i am running this on windows 2k (sp3) (i know i should be running on a real operating system: linux/unix, not this microsoft crap; i have no one to blame but myself for sticking with windows :(...), with 1.7 gb of free memory (that's why I am assuming problems are not coming from virtual memory...) thanx...

[ZoogieZork]

If it's only three arrays, is there any way you can allocate those three at the start of the program, then just re-use them? - Mike