stanislav.bezkorovainyi's blog

Question about performance of pointers
By stanislav.bezkorovainyi, history, 7 years ago, In English

I tried to test perfomance of different approaches to build and use trie data structure.

I used 706D - Vasiliy's Multiset to test my versions of tries on it.

The question is: Why does approach with pointers takes 2 times more memory than one with static array? As I know, a pointer stores an address of a variable, so it shouldn't take that much memory.

Here are my submissions:

Pointer approach: 40063381

Static array approach: 40063561

Any suggestions are welcomed!

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7 years ago, # |
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Sorry for my mistakes in English (if there were any)

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7 years ago, # |
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Storing a pointer takes 4 or 8 bits depending on whether you use 32-bit or 64-bit OS.

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7 years ago, # |
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Most probably, it is caused by memory fragmentation.

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7 years ago, # |
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Nice problem, thanks! You can try your trie on this problem, very interesting, but I solved it with sort + implicit trie + binary search in O(n * log(n) * WORD_WIDTH) time, with your trie you can get O(n * WORD_WIDTH) time.

About 64-bits pointers and 32-bit pointers. I think that you can't solve this problem with persistent segment tree if you will use pointers against indexes in array — my friend gets memory limit exceeded, but you can check it and write to me. My solution on array against 64-pointers (russian comments, sorry).

English statement of 4498 e-olymp
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