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gnu hash_map very slow.


From: Terry IT
Subject: gnu hash_map very slow.
Date: Wed, 8 Oct 2008 10:49:18 -0700 (PDT)
User-agent: G2/1.0

i tried inserting around 2*10^5 elements in hash_map it was fast. Next
when i did some erasuring it was very slow. The same input on map took
2 secs where g++ hash_map takes 40 secs.  What i could figure out from
this is that hash_map are only good for insertion and lookups rather
than removal.

a) Why is it so ? What are the hash functions used.

b) Is tr1/unordered_map any different from hash_map of g++. I didn't
notice much change in runtime between hash_map and unordered_map . Do
they use the same hash function.



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