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Re: Impressive improvement in std::vector when dealing with raw memory. [message #59190 is a reply to message #59179]

Sat, 19 November 2022 22:04

Lance is currently offline

Lance
Messages: 656
Registered: March 2007

Contributor

Morale of basic_string story: sometimes (more than occasionally), it's possible to make a class trivially relocatable by slightly changing your design.

While I did not do a speed comparison of the underlying memory copy facilities (just move a volume of bytes around repeatedly for certain times) of std::vector and Upp::Vector, an intuitive explanation of Upp::Vector's performing well on small memory size and lagging behind when the memory block getting large is the difference in their respective memory management strategies.

A std::vector doubles it's capacity at each growth (until out of memory etc) while a Upp::Vector grows by 1/3 of its current capacity. Upp::Vector mitigates its supposedly more frequent allocation/relocation by doing TryRealloc, which, when success, housed objects relocation can be avoided. While the latter has more chances to succeed when allocated memory block is small (thus results in a amortized gain over std::vecotr ), it tends to fail more often when the allocated memory block is big. In which case more frequent reallocation and relocation plus additional cost on (almost bound to fail) TryRealloc(will have to lock some mutex at least) drag the overall performance.

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[Message index]

		Impressive improvement in stl::vector when dealing with raw memory. By: Lance on Mon, 14 November 2022 01:48
		Re: Impressive improvement in stl::vector when dealing with raw memory. By: pvictor on Mon, 14 November 2022 09:46
		Re: Impressive improvement in stl::vector when dealing with raw memory. By: Lance on Mon, 14 November 2022 14:31
		Re: Impressive improvement in stl::vector when dealing with raw memory. By: Lance on Mon, 14 November 2022 14:52
		Re: Impressive improvement in stl::vector when dealing with raw memory. By: Lance on Mon, 14 November 2022 15:28
		Re: Impressive improvement in std::vector when dealing with raw memory. By: Lance on Mon, 14 November 2022 17:24
		Re: Impressive improvement in std::vector when dealing with raw memory. By: Lance on Tue, 15 November 2022 15:58
		Re: Impressive improvement in std::vector when dealing with raw memory. By: Lance on Sat, 19 November 2022 22:04
		Re: Impressive improvement in std::vector when dealing with raw memory. By: Lance on Sun, 20 November 2022 01:50
		Re: Impressive improvement in std::vector when dealing with raw memory. By: mirek on Mon, 21 November 2022 16:34
		Re: Impressive improvement in std::vector when dealing with raw memory. By: Lance on Wed, 23 November 2022 00:39

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