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68: How much memory will my TP program require?A: Get MAPMEM.EXE from ftp://garbo.uwasa.fi/pc/memutil/tsrcom35.zip and put the following code within your Turbo Pascal program: Program faq; uses Dos; : SwapVectors; Exec (GetEnv('comspec'), '/c mapmem'); Swapvectors; Then you'll see a MAPMEM output something like this Psp Cnt Size Name Command Line Hooked Vectors ---- --- ------ ---------- ------------------- -------------- 2 26,896 DOS 0694 2 3,392 COMMAND 2E 1 64 ---free--- 0776 2 1,488 MARK scrollit 07D6 2 70,816 FAQ FF 1923 3 2,752 command 22 23 24 19D2 2 549,712 ---free--- 655,344 ---total-- The memory requirement of your program FAQ.PAS is 70,816. Do not confuse this figure with the physica size of your program. The memory requirement affected among other things by the Memory Allocation Sizes Directive. For example you might have {$M 16384,0,50000} -Date: Sun, 12 Jun 1994 10:22:18 -From: dmurdoch@mast.queensu.ca (Duncan Murdoch) -Newsgroups: comp.lang.pascal -Subject: Re: How much memory will my TP program require? I think this is a hard question, and probably needs a longer answer than you gave. Yours isn't quite right, because TP will allocate memory that it doesn't need if you set the heapmax parameter too high. Your program will run in less memory than MAPMEM reports. Here's a quick attempt at it: TP DOS programs use memory in 4 or 5 blocks: fixed code, static data, the stack, sometimes overlaid code, and the heap. TP Windows programs add a local heap to this list, but don't use overlays. The discussion below deals with real mode DOS programs. The size of the code is determined by which procedures and functions you use in your program. In DOS, if you don't use overlays, this is all fixed code, and the size is reported as "Code size" in the Compile| Information listing in the IDE. The ways to reduce it are to use fewer procedures or make them smaller, or move them to overlays. Static data consists of all the global variables and typed constants in every unit. It is reported as "Data size" in the Compile|Information listing. You can reduce it by declaring fewer or smaller variables. If you use the $O directive to move code to overlays, then those units won't count as part of your fixed code needs. You will need an overlay buffer at run-time; by default, it's the size of the largest unit you use, but normally you'll change the size with OvrSetBuf. It's difficult to work out the best size of this block except by trial and error: if your program spends too much time swapping, then make it larger; if you run out of memory, make it smaller. You'll need to use the .MAP file (see the Options| Linker dialog to create one) to find the size of each unit. Remember to subtract the size of overlaid units from the reported "Code size" when working out the size of fixed code. The stack is used for local variables in procedures. Its size is controlled by the first parameter to the $M directive; the default size is 16K. It's hard to predict exactly how much stack space your program will use. One way is to keep reducing the value until your program aborts with a stack overflow, then use a slightly larger value. Another way is to fill the stack with a fixed value at the start of your program, and at the end, see how many values were changed. Again, it's a good idea to allow for a margin of safety, because hardware interrupts will use this space, and their size is hard to predict. The heap is where New and Getmem get their allocated memory. The size is controlled by the 2nd and 3rd parameters to the $M directive. The heapmin value will always be allocated; if extra memory is available, your program will ask for as much as possible, up to heapmax. If not enough memory is available to load all your fixed code, data, stack and heapmin, DOS will refuse to load your program. You have nearly complete control over the size of the heap that you need, determined by how much you use New and Getmem. The only exception is that some of the standard units use heap space; GRAPH and all the TurboVision units are examples. To find how much your program actually uses, you can reduce Heapmax until it fails, fill the heap with a special value and look for changes, or monitor the value of HeapPtr as your program progresses. |
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