[cfe-dev] [libcxx] Extending the behavior of std::hash in libc++

Geoff Pike via cfe-dev cfe-dev at lists.llvm.org
Tue Dec 8 19:37:47 PST 2015


On Tue, Dec 8, 2015 at 5:07 PM, Justin Lebar <jlebar at google.com> wrote:
>> The thing I would like is a more explicit discussion of hash function families, and the ability to select from a family.
>
> How would this be different from the hashtable / bloom filter hashing
> in a random number into the beginning or end of the bitstream?  Is the
> idea that we could be more efficient than this, or that we could get
> better hashes if we had explicit support for seeding the hash?

Would the container writer be able to manipulate a bitstream?
Currently, the container just gets a hash function to call, whose
input is a key and whose output is size_t.

Also, the ideal number of bits to prepend, if you're going that route,
would be different for different hash function families. It seems more
logical to me to make the interface more explicit about the existence
of hash function families.

Geoff


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