Do not re-hash already hashed keys disambiguator and struct identity maps #647
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Veykril
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Did you do any perf measurements on ra to verify that the extra complexity and memory usage is worth it? |
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Not yet, until r-a can use the master branch salsa, checking anything against r-a is kind of a pain as I'd need to work against david's fork I believe. Either way I'd consider the complexity here rather minor and self-contained (I can clean it up a bit and make it more descriptive if desired) while omitting unnecessary work. So even with perf measurement it should be clear that this skips work imo |
…maps Additionally newtypes these maps
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src/tracked_struct.rs
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| // conceptually, this contains an `IdentityHash`, but using the type directly will grow the size | ||
| // of if this struct by a word due to unusable padding, so we store the fields directly instead. | ||
| /// Index of the tracked struct ingredient. |
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two nits:
- Phrasing
- Considering moving this comment up to
Identity's doc comment?
| // conceptually, this contains an `IdentityHash`, but using the type directly will grow the size | |
| // of if this struct by a word due to unusable padding, so we store the fields directly instead. | |
| /// Index of the tracked struct ingredient. | |
| /// Index of the tracked struct ingredient. | |
| /// | |
| /// Conceptually, this contains an `IdentityHash`, but using `IdentityHash` directly will grow the size | |
| /// of this struct struct by a `std::mem::size_of::<usize>()` due to unusable padding. To avoid this increase | |
| /// in size, `Identity` stores the fields directly instead. |
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I put it outside of the doc comment as this is just an implementation detail, it is not relevant to the ingredient_index field
src/tracked_struct.rs
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| let eq_module_hash = |k: &Identity| { | ||
| k.ingredient_index == key.ingredient_index && k.disambiguator == key.disambiguator | ||
| }; | ||
| let entry = self.map.raw_entry_mut().from_hash(key.hash, eq_module_hash); |
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consider inlining eq_module_hash?
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Oh, that was supposed to be eq_modulo_hash. I prefer keeping it outside as it documents what we check (also the formatting like this is more readable imo)
src/tracked_struct.rs
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| let eq_module_hash = |k: &Identity| { | ||
| k.ingredient_index == key.ingredient_index && k.disambiguator == key.disambiguator | ||
| }; |
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consider inlining eq_module_hash?
src/tracked_struct.rs
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| let eq_module_hash = |k: &IdentityHash| k.ingredient_index == key.ingredient_index; | ||
| let entry = self.map.raw_entry_mut().from_hash(key.hash, eq_module_hash); |
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consider inlining eq_module_hash?
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Additionally newtypes these maps.
We got no reason to hash what we already have hashed! (This does need hashbrown as std doesn't stably expose the required API yet)