Hierarchical Control Flow / Control Flow Regions #1404
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phschaad
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alexnick83
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Oct 25, 2023
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Looks good in general. The changes are many, and we will need some time to get used to them and clean up issues that may arise. Since we recently had a new release that non-developers can use, I am in favor of merging to master ASAP to uncover problems that tests don't expose.
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| for block in cf.nodes(): | ||
| if isinstance(block, dace.SDFGState): |
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If the block is not an SDFGState, don't we also need to call replace on the block itself?
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Agreed @phschaad is there a need to replace inside a block? Does it have its own properties? Right now it's only is_collapsed and label, but I imagine loops would have other symbols in them.
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In general yes, it would need such a replacement as well. However, this is only replace_datadesc_names. There are currently no plans of having blocks (other than states) access data descriptors directly. They should all operate on symbols.
tbennun
requested changes
Oct 30, 2023
| e.data.replace_dict(repl, replace_keys=False) | ||
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| for block in cf.nodes(): | ||
| if isinstance(block, dace.SDFGState): |
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Agreed @phschaad is there a need to replace inside a block? Does it have its own properties? Right now it's only is_collapsed and label, but I imagine loops would have other symbols in them.
tbennun
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Nov 2, 2023
phschaad
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Nov 27, 2023
This PR adds `LoopRegion`s to SDFGs. This forms the second core element of the [plan to make loops first class citizens of SDFGs](https://github.com/orgs/spcl/projects/10). `LoopRegion`s are a special class of `ControlFlowRegion`s that represent different types of loops, meaning the control flow region inside them is executed a parametric number of times. A `LoopRegion` _must_ have a conditional expression that determines whether the region is executed or not. It may additionally have: - an initialization expression that is run when the region is first executed (even if the condition to execute its contents does not hold) - an update expression, executed each time the execution of the region contents is finished - a flag indicating that it's inverted, meaning the contents are executed once before the condition is checked (condition is checked again after every execution) - a set of control flow blocks in its contents that, when reached, finish the execution of the region and do not execute it again even if the condition still holds (equivalent to `break` in C/Python) - a set of control flow blocks that end the execution of its contents and execute the update statement if there is one. After this, the condition is checked again and the contents may be run again (equivalent to `continue` in C/Python) For more general information on control flow regions please refer to [the documentation](https://spcldace.readthedocs.io/en/latest/sdfg/ir.html#elements) or the [PR that introduced them](#1404). An example of a tripple loop nest of regular for loops can be seen in the GEMM program below, showing that a proof-of-concept visualization for the introduced concepts is already available in the latest release version of the [VSCode extension](https://marketplace.visualstudio.com/items?itemName=phschaad.sdfv) (version 1.6.0 and upwards):  As outlined by the [project plan](https://github.com/orgs/spcl/projects/10), these `LoopRegion`s are currently _not_ being used by any frontend. They can, however, already be manually used through the SDFG builder API. According to plan, most passes and transformations are not currently able to handle the use of such `LoopRegion`s yet, so their use is still highly experimental. To allow traditional transformations and passes to work, as well as to be able to generate codes for SDFGs containing `LoopRegion`s, a compatibility pass (`InlineLoopRegions`) is available, together with a utility function `dace.sdfg.utils.inline_loop_blocks` that inlines any `LoopRegion`s to traditional state machine loops. In summary, the PR includes: - [x] Add `LoopRegion`s to SDFGs, a special control flow region to represent loops - [x] Pass / Utility function to remove all loop regions from a graph, turning them back into regular state machine loops (a.k.a., inlining) - [x] Tests for inlining of loops - [x] Tests for the functional correctness of different types of loops (regular for, while, do-while, do-for) and nested loops (gemm - tripple nested loop) --------- Co-authored-by: Tal Ben-Nun <tbennun@users.noreply.github.com>
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Refactors the SDFG list and SDFG ids to a more general CFG list and CFG id. This change provides a further step towards compatibility with the [hierarchical, multi-level SDFGs](#1404). The change is accompanied by a deprecation warning on the old interfaces (`sdfg_list`, `sdfg_id`, `reset_sdfg_list`, and `update_sdfg_list`). Until removal, the legacy methods continue to work as expected for single level SDFGs. --------- Co-authored-by: alexnick83 <31545860+alexnick83@users.noreply.github.com>
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This introduces hierarchical control flow to SDFGs in the form of control flow regions.
The number of new tests in this PR is currently limited since it only introduces the basic structure change and should hence be covered by existing tests. It is currently not yet possible to actually use or interact with hierarchical SDFGs in any manner besides using the SDFG creation API, since even validation is not yet capable of properly interpreting such an SDFG. This will be handled piece-wise in a number of subsequent PRs (see https://github.com/orgs/spcl/projects/10 for details and the roadmap).
In this PR:
is_start_statedeprecationNote: this does not change anything about how you interact with SDFGs and provides complete backwards compatibility. No hierarchical control flow regions can currently be added, since there is no concrete implementation that extends them yet besides SDFGs themselves.