This project provides alternative implementations of things like Cats's StateT that are specifically designed for use in situations where performance is important. For example, we'd like to use StateT in Finch, but our initial experiments suggest that the overhead the version in Cats would introduce would not be consistent with Finch's goals.

The StateT implementation provided by this project is mostly source-compatible with Cats's, but it takes a different approach to providing stack safety, and it uses methods in places where the Cats version uses FunctionN values. The initial benchmarks suggest that this approach may get us closer to something that would work for Finch (higher numbers are better):

Benchmark                        Mode  Cnt    Score   Error  Units
StateTBenchmark.traverseStateC  thrpt   40   61.313 ± 0.507  ops/s
StateTBenchmark.traverseStateM  thrpt   40  131.301 ± 1.728  ops/s

And allocation rates (lower is better):

Benchmark                                           Mode  Cnt         Score     Error   Units

StateTBenchmark.traverseStateC:gc.alloc.rate.norm  thrpt   20  19767449.565 ±  50.382    B/op
StateTBenchmark.traverseStateM:gc.alloc.rate.norm  thrpt   20  13126749.061 ±  27.103    B/op

This is currently an experimental project. It is not published anywhere, and may never be. If you'd like to contribute, please see the open issues or get in touch on Twitter.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this software except in compliance with the License.

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.