Remove one level of indirection for boxed ChaseLev #74
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Note: if this looks like a good idea, we should also do the same for the |
Previously, we had an `IORef` holding a mutable vector. We can
remove one level of indirection by using an `UnliftedArray` (i.e.,
an `ArrayArray#`) to hold the array instead.
Before:
ChaseLevDeque -> MutVar# -> MVector -> Array#
Now:
ChaseLevDeque -> ArrayArray# -> Array#
Note: we previously got the vector size from the `MVector`; now
we get it from the `Array#`. In many applications `MVector`s unbox,
so getting sizes from them is faster than getting them from `Array#`s.
However, this is *not* such an application: we're continually storing
and retrieving the vectors.
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The `ArrayArray#` solution was fairly pretty, but `ArrayArray#`s have card-marking logic we really don't need. We can `unsafeCoerce#` our way into using a `MutVar#` instead. It would be much nicer if GHC exposed a proper unlifted `MutVar#`, but this way seems to work.
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I'm having trouble working out how to update the CI with the necessary |
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@RyanGlScott , can you maybe help me figure out this CI issue? |
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@wangbj, Ryan Scott thought you might be able to review this. |
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@treeowl I’ll try, btw the ci issue should be fixed if you merge master branch |
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Previously, we had an
IORef(holding anMVector. We canremove one level of indirection by sticking an
Array#directly into anIORef.That's not officially supported, but it does work (Edward Kmett has used a similar trick).
Before:
Now:
Note: we previously got the vector size from the
MVector; nowwe get it from the
Array#. In many applicationsMVectors unbox,so getting sizes from them is faster than getting them from
Array#s.However, this is not such an application: we're continually storing
and retrieving the vectors. I expect the array size checks will be cost the same
as they did before, but array indexing should be faster.