[scan] support gen_schema for scan #158864
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[ghstack-poisoned]
This was referenced Jul 22, 2025
🔗 Helpful Links🧪 See artifacts and rendered test results at hud.pytorch.org/pr/158864
Note: Links to docs will display an error until the docs builds have been completed. ✅ No FailuresAs of commit 3f98bb4 with merge base 5a40c57 ( This comment was automatically generated by Dr. CI and updates every 15 minutes. |
This was referenced Jul 22, 2025
[ghstack-poisoned]
[ghstack-poisoned]
We don't want to allow scan's combine_fn to mutate its inputs. The semantic of the mutation can be confusing. For example: ```python def combine_fn(init, x): ``` If combine_fn mutates init, only first iteration mutates init, the rest of the iterations mutates the previous carry, which is an intermediate result. This is kind of a weird semantic because the only observable mutation is for init, which can be done outside of the combine_fn. If combine_fn mutates x, where x is a slice of scanned inputs (i.e. xs), this pattern is more meaningful but we've not seen any use case yet. [ghstack-poisoned]
We don't want to allow scan's combine_fn to mutate its inputs. The semantic of the mutation can be confusing. For example: ```python def combine_fn(init, x): ``` If combine_fn mutates init, only first iteration mutates init, the rest of the iterations mutates the previous carry, which is an intermediate result. This is kind of a weird semantic because the only observable mutation is for init, which can be done outside of the combine_fn. If combine_fn mutates x, where x is a slice of scanned inputs (i.e. xs), this pattern is more meaningful but we've not seen any use case yet. [ghstack-poisoned]
This was referenced Jul 24, 2025
zou3519
approved these changes
Jul 31, 2025
We don't want to allow scan's combine_fn to mutate its inputs. The semantic of the mutation can be confusing. For example: ```python def combine_fn(init, x): ``` If combine_fn mutates init, only first iteration mutates init, the rest of the iterations mutates the previous carry, which is an intermediate result. This is kind of a weird semantic because the only observable mutation is for init, which can be done outside of the combine_fn. If combine_fn mutates x, where x is a slice of scanned inputs (i.e. xs), this pattern is more meaningful but we've not seen any use case yet. [ghstack-poisoned]
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Stack from ghstack (oldest at bottom):
We don't want to allow scan's combine_fn to mutate its inputs. The semantic of the mutation can be confusing. For example:
If combine_fn mutates init, only first iteration mutates init, the rest of the iterations mutates the previous carry, which is an intermediate result. This is kind of a weird semantic because the only observable mutation is for init, which can be done outside of the combine_fn.
If combine_fn mutates x, where x is a slice of scanned inputs (i.e. xs), this pattern is more meaningful but we've not seen any use case yet.