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| Original file line number | Diff line number | Diff line change |
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| title = "argmin 0.8.0 and argmin-math 0.3.0 released" | ||
| description = "" | ||
| date = 2023-01-28T00:00:00+00:00 | ||
| updated = 2023-01-28T00:00:00+00:00 | ||
| draft = false | ||
| template = "blog/page.html" | ||
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| [taxonomies] | ||
| authors = ["Stefan Kroboth"] | ||
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| [extra] | ||
| +++ | ||
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| <b>argmin</b> is a Rust library which offers a range of numerical optimization methods and a framework for | ||
| developing optimization algorithms. <b>argmin-math</b> is a trait-based abstraction layer for mathematical operations, | ||
| which makes argmin compatible with various math backends such as [ndarray](https://crates.io/crates/ndarray) and | ||
| [nalgebra](https://crates.io/crates/nalgebra) (or your own backend). | ||
| For details about the design of argmin and its features I suggest having a look at | ||
| [the website](https://argmin-rs.org), | ||
| [the book](https://argmin-rs.org/book), | ||
| [Github](https://github.com/argmin-rs/argmin), | ||
| [crates.io](https://crates.io/crates/argmin) and | ||
| [lib.rs](https://lib.rs/crates/argmin). | ||
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| This is a short summary of the changes in argmin 0.8.0 and argmin-math 0.3.0. | ||
| Both releases include breaking API changes; however upgrading from the previous versions should hopefully be fairly smooth. | ||
| Don't hesitate [to get in touch](https://github.com/argmin-rs/argmin/issues) in case you run into problems during upgrading. | ||
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| ## argmin 0.8.0 | ||
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| #### Improved termination handling | ||
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| The solver state contains a `TerminationReason` enum which indicates why the solver terminated. | ||
| The enum variants offered in previous versions of argmin were either applicable to all solvers or were solver-specific. | ||
| [@relf](https://github.com/relf) [rightfully pointed out](https://github.com/argmin-rs/argmin/issues/305) that these variants weren't ideal: | ||
| For instance, it included an awkward variant `NotTerminated` and a couple of variants could be summarized as `Converged`. | ||
| Whenever a `Ctrl+C` was intercepted, the reason would be `Aborted`, which is suboptimal because a solver could also abort | ||
| due to other reasons. | ||
| In the discussion we decided to change the `TerminationReason` enum to the following: | ||
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| ```rust | ||
| pub enum TerminationReason { | ||
| /// Reached maximum number of iterations | ||
| MaxItersReached, | ||
| /// Reached target cost function value | ||
| TargetCostReached, | ||
| /// Algorithm manually interrupted with Ctrl+C | ||
| KeyboardInterrupt, | ||
| /// Converged | ||
| SolverConverged, | ||
| /// Solver exit with given reason | ||
| SolverExit(String), | ||
| } | ||
| ``` | ||
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| The first two are potential outcomes of two checks performed by the `Executor` for every solver. | ||
| `KeyboardInterrupt` replaces `Aborted` and is only used for `Ctrl+C`. | ||
| `SolverConverged` indicates a successful optimization run and `SolverExit(String)` is used for | ||
| cases where the solver stopped for a solver-specific reason specified by a string. | ||
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| The awkward `NotTerminated` was dropped and instead a new enum `TerminationStatus` is introduced: | ||
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| ```rust | ||
| enum TerminationStatus { | ||
| NotTerminated, | ||
| Terminated(TerminationReason) | ||
| } | ||
| ``` | ||
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| This enum is stored in the state instead of `TerminationReason`. | ||
| It can be obtained from an `OptimizationResult` via the solver state: | ||
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| ```rust | ||
| // of type &TerminationStatus | ||
| let status = result.state().get_termination_status(); | ||
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| // ... or ... | ||
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| // of type Option<&TerminationReason> | ||
| let reason = result.state().get_termination_reason(); | ||
| ``` | ||
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| Both methods are part of the `State` trait and as such available for all available states. | ||
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| Note that this is a breaking change and as such you may have to adapt your code, in particular if you use the returned | ||
| termination reason. | ||
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| Huge thanks to [@relf](https://github.com/relf) for the fruitful discussion and for doing all the heavy lifting! | ||
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| #### Changes to the observer interface | ||
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| In the past, values sent to the observers were only `dyn Display`, which means they could effectively only be turned into strings. | ||
| To get the actual value one had to parse the strings into a given type, which isn't great (to put it mildly). | ||
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| Therefore I decided [to make the values sent to the observers typed](https://github.com/argmin-rs/argmin/pull/269) and | ||
| added support for 64bit floats, signed and unsigned 64bit integer, Booleans and Strings via the `KvValue` enum: | ||
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| ```rust | ||
| pub enum KvValue { | ||
| Float(f64), | ||
| Int(i64), | ||
| Uint(u64), | ||
| Bool(bool), | ||
| Str(String), | ||
| } | ||
| ``` | ||
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| The actual values can be retrieved via the getters `get_float`, `get_int`, `get_uint`, `get_bool` and `get_string`, | ||
| which return `Some(<inner_value>)` if the `KvValue` is of the appropriate type and `None` otherwise. | ||
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| The `make_kv!` macro used in solvers to construct the Key-Value store was renamed to `kv!`. | ||
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| These changes will only affect you if you wrote an observer or solver yourself. | ||
| All observers shipped with argmin should continue to work as before. | ||
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| #### Other | ||
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| * Implementing the `Solver` trait for a solver does not require anymore that the solver implements `serde::Serialize` when the `serde1` feature is enabled. | ||
| This was a remnant of an earlier design of the `Solver` trait found by [@relf](https://github.com/relf). | ||
| Note that checkpointing requires solvers to be serializable! | ||
| Therefore, despite lifting this requirement, it is still recommended that solvers are (de)serializable if possible. | ||
| * The check whether an optional target cost is reached is now based on the best cost function value so far rather than the current cost function value ([@relf](https://github.com/relf)) | ||
| * Added a `full` feature which activates all features. | ||
| * Added a particle swarm optimization and L-BFGS example using the nalgebra backend. | ||
| * Elapsed time is now computed using `as_secs_f64` ([@TheIronBorn](https://github.com/TheIronBorn)) | ||
| * Internally uses argmin-math 0.3.0, so make sure to update both! | ||
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| ## argmin-math 0.3.0 | ||
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| With this release all backends finally implement all math-related traits, meaning that every backend now works with every solver. | ||
| The only exception to this is the `vec` backend, which does not implement `ArgminInv` and as such does not | ||
| work with (Gauss-)Newton methods. | ||
| I've spent multiple days tediously implementing all missing traits and adding tests for every implementation | ||
| (eventually reaching 100% test coverage). | ||
| [@hypotrochoid](https://github.com/hypotrochoid) implemented the `ArgminRandom` trait for the ndarray backend | ||
| and with that kicked off this entire endeavour. Thanks! | ||
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| Apart from that support for nalgebra 0.32 was added and ndarray-linalg was updated from version 0.14 to 0.16 for | ||
| the ndarray v0.15 backend. | ||
| Therefore you may have to update ndarray-linalg as well. | ||
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| Upgrading to version 0.3.0 of argmin-math should be smooth for most cases. | ||
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| ## Other news | ||
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| argmin is not only a collection of optimization algorithms but also aims to be a framework which facilitates | ||
| the development of optimization algorithms. | ||
| Solvers implemented using argmin get features such as checkpointing, observers and support for various math backends for free. | ||
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| However, I have not seen any use of this feature outside of argmin itself up until recently, when [@relf](https://github.com/relf) | ||
| made his [egobox-ego solver](https://crates.io/crates/egobox-ego) | ||
| [compatible with argmin](https://github.com/relf/egobox/pull/67). | ||
| This is very exciting for me as this led to valuable feedback on the design of argmin and I hope that others will follow | ||
| that example and make their solvers compatible with argmin. | ||
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| <br> | ||
| <script async defer src="https://buttons.github.io/buttons.js"></script> | ||
| <p align="center"> | ||
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| <a class="github-button" href="https://github.com/argmin-rs/argmin/fork" data-icon="octicon-repo-forked" data-size="large" data-show-count="true" aria-label="Fork argmin-rs/argmin on GitHub">Fork</a> | ||
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| </p> |