Re: CUDA Sorting

Greg Stark <stark(at)mit(dot)edu> writes:
> That said, to help in the case I described you would have to implement
> the tapesort algorithm on the GPU as well.

I think the real problem would be that we are seldom sorting just the
key values. If you have to push the tuples through the GPU too, your
savings are going to go up in smoke pretty quickly ...

FWIW, I tend to believe a variant of what Greg Stark said upthread:
there would surely be some win from reducing the impedance mismatch for
comparison functions. In concrete terms, there would be no reason to
have tuplesort.c's myFunctionCall2Coll, and maybe not
inlineApplySortFunction either, if the datatype-specific comparison
functions had APIs that were closer to what sorting wants rather than
following the general SQL-callable-function API. And those functions
cost a *lot* more than a one-instruction comparison does. But it's very
much more of a stretch to believe that inlining per se is going to do
much for us, and even more of a stretch to believe that getting a
separate processor involved is going to be a win.

regards, tom lane