CODEWITHSUNDEEP
c++hash
SuperString
SuperString

Reputation: 22519

How to find table size and memory consumption of STL hash_map?

I want to know how stl hash_map is implemented. How do I find out what the table size is and the memory space the map consumes? This is in C++.

Upvotes: 1

Views: 1670

Answers (3)

Terry Mahaffey
Terry Mahaffey

Reputation: 11981

There is no such thing as an "stl hash_map". There is an unordered_map in TR1, but I assume you're not using that or you would have said unordered_map.

As someone pointed out, unordered_map has "bucket_count" to determine the number of buckets. You can iterate over each bucket, get it's size ("bucket_size(size_t bucket_num)"), multiply that by the size of a pair of key and values, and add them all up to give you a rough estimate of the memory used. There may be non-portable ways which are implementation defined. It will obviously be implemention defined for whatever hash_map class you're using.

Upvotes: 2

avakar
avakar

Reputation: 32635

Try bucket_count.

Upvotes: 0

duffymo
duffymo

Reputation: 308763

This blog entry on C++ STL Hash Containers and Performance is a good looking explanation of STL hash map. See if it helps you.

Upvotes: 1

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