Cost of memory [de]allocation and potential compiler optimizations (c++) -

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is cost of memory [de]allocation defined? if cost depends upon specific compiler being used, there general way memory [de]allocation implemented such can reasonably assume cost?

is compiler able optimize following code such call 'new' done once?

char * arr = null; (size_t = 0; < 5000000000; ++i) {     arr = new char[100000000]     ... // process things here     delete []arr; }

the compiler not able perform optimization. @ lowest level, storage allocation boils down calls library functions such malloc (and, 1 layer deeper, os apis). compiler it's not safe assume individual malloc/free pairs can left out , storage reused because implementation should outside optimizer's scope.

apart that, don't think job optimizer. that's you, programmer, can without special efforts.

there no standardized cost memory allocation/deallocation. generally, allocation/deallocation times may vary (for example take longer if user-space heap implementation forced fetch fresh pages os kernel's memory manager).

a reasonable rule of thumb small allocations faster larger ones , allocations should slower de-allocations.


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