Re: perfomance of clear vs swap

[Paul Pluzhnikov]

krishanu.debnath@gmail.com writes:

> I have a call to hash_map::clear() function which takes long time.

It is somewhat likely that you are mis-interpreting the results
that you observed.

It is hard to imagine a situation in which creating a hash_map
takes less time than clear()ing it.

Using g++4.0.0, creating a 10,000,000 entry hash_map takes 116
seconds on my machine; clearing via either clear() or swap() with
temporary takes 8 seconds.

> Now runtime drops significantly, 10 fold less.
> What's exactly cause this run time reduction?

User error, most likely.

If you are convinced that you really see what you claim to see,
post a complete compilable test case that demonstrates that.

Cheers,
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