feat: Improve TASO cost function and rewrite strategies #154
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aborgna-q
approved these changes
Oct 3, 2023
src/rewrite/strategy.rs
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| /// | ||
| /// The minor cost to break ties between equal CX counts is the number of | ||
| /// quantum gates. | ||
| pub type NonIncreasingCXCountStrategy = |
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The name is a bit detached from the actual definition. Any non-inc strategy with static cost functions will type with this alias.
The default_cx call is the one that introduces the actual CX semantics.
Do you need the alias?
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No you're right. I'll remove it.
src/rewrite/strategy.rs
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| /// The cost function must return a value of type `Self::OpCost`. All op costs | ||
| /// are summed up to obtain a total cost that is then compared using the | ||
| /// threshold function. | ||
| pub trait ExhaustiveThresholdStrategy { |
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Sorry, this ended up being much bigger than expected. If you have any suggestions to simplify it, I'll gladly take them.
I have added a rewrite strategy that considers not only two-qubit gate count, but also breaks ties with total gate count. I think this should make the optimisation landscape less flat overall.
I've also taken the opportunity to make the optimisation cost function a data of the rewrite strategy, so that it no longer has to be passed separately to TASO.