Add support for device vectors through a workaround#23
Add support for device vectors through a workaround#23RyanMoulday wants to merge 1 commit intotjhei:masterfrom
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Can you add a test or two please?
| assert_dof_handler(dof_handler); | ||
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| const unsigned int min_level = dst.min_level(); | ||
| const unsigned int min_level = transfer.min_level(); |
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Oops, this is a mistake, this must have changed in the commits since I made the PR last time. I copied and pasted the whole file from my previous PR over and it must have overwritten this change. Should have double checked, I restored this to its current version.
| LinearAlgebra::distributed::Vector<Number, dealii::MemorySpace::Host>; | ||
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| MGTransferMatrixFree( | ||
| const MGLevelObject<MGTwoLevelTransfer<dim, VectorTypeHost>> &mg_transfers, |
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It is a bit surprising that we initialize with host vectors here, right? That would mean if we make this work on device later, user code needs to change?
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Yes this is a good point but rather annoying to work around. These inputs are used to initialize the underlying MGTransferMatrixFree class that is defined on the host which does the "workaround" part of this. To switch these to be device elements we would need some method by which we could convert them to equivalent objects on the host which I'm not sure how easy or feasible that is.
| dst_host; | ||
| MGLevelObject<VectorTypeHost> src_host(src.min_level(), src.max_level()); | ||
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| copy_to_host(dst_host, dst); |
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This is not safe to remove directly because "dst.copy_locally_owned_data_from()" inside copy_from_mg called on the host transfer complains that dst is inappropriately sized. I believe this is because it is initialized but never partitioned correctly and the copy_to_host() call is accomplishing this.
Once I partitioned the vector this was safe to remove.
| VectorTypeHost dst_host; | ||
| VectorTypeHost src_host; | ||
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| copy_to_host(dst_host, dst); |
| VectorTypeHost dst_host; | ||
| VectorTypeHost src_host; | ||
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| copy_to_host(dst_host, dst); |
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…to host to execute transfer before sending back to device.
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| // ------------------------------------------------------------------------ | ||
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| // Check MGTransferMatrixFree by comparison with MGTransferPrebuilt on a |
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Update this comment to include device
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| // build host reference | ||
| MGTransferMatrixFree<dim, Number, dealii::MemorySpace::Host> | ||
| transfer_host(mg_constrained_dofs); |
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It looks like you are using local smoothing multi grid here. Not wrong, but portable MatrixFree is currently only doing global coarsening.
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