Ensure NativeFunctions.h codegen output is deterministic (#58889)

bdhirsh · facebook-github-bot · commit 32273e806a74 · 2021-05-25T16:33:03.000-07:00
Summary: Pull Request resolved: #58889 fixes #58796 Planning on re-testing locally tomorrow morning to confirm, but this change should fix the non-determinism in the codegen output that was causing `ccache` not to re-use its cached output. I built from the commit referenced in #58796 a few times and ran `diff -Naur` on the codegen output in `build/aten/src/ATen`. After a few tries, `NativeFunctions.h` had a few diffs. The diffs were all related to the ordering of functional/inplace/out variants of a NativeFunctionGroup, which looked non-deterministic. That looks like it's coming from my calling `set()` to filter out duplicate NativeFunction declarations. The earlier version of the codegen also called `set()` to filter out duplicates, but it did so individually for each `NativeFunction` object, before merging the groups (I'm not too sure why this didn't introduce non-determinism before. though). With the refactor from #57361, we're calling `set()` on the declarations from every operator for a given DispatchKey, which is probably what introduced the nondeterminism. Test Plan: Imported from OSS Reviewed By: gchanan Differential Revision: D28675941 Pulled By: bdhirsh fbshipit-source-id: bb66de00aafeeb9720d85e8156ac9f7539aed0d6
diff --git a/tools/codegen/gen.py b/tools/codegen/gen.py
@@ -1026,7 +1026,7 @@ def make_file_manager(install_dir: str) -> FileManager:
         'native_function_declarations': list(concatMap(
             # Convert to a set first to remove duplicate kernel names.
             # Backends are allowed to repeat kernel names; only generate the declaration once!
-            lambda f: list(set(concatMap(
+            lambda f: list(OrderedDict.fromkeys(concatMap(
                 lambda backend_idx:
                     dest.compute_native_function_declaration(f, backend_idx),
                 backend_indices.values()))),
