Add CONTRIBUTING.md for bpe explaining project structure and benchmar…

…k instructions

crates/bpe/CONTRIBUTING.md

@@ -0,0 +1,39 @@
+# Contributing
+
+Here are specific details that are useful when you want to contribute to the BPE crates.
+Make sure to read the repository's [contribution guidelines][contributing] as well.
+
+## Project structure
+
+This project has a slightly unusual structure to resolve some dependency issues.
+
+- This directory contains `bpe`, the BPE code itself.
+- A sibling directory contains `bpe-openai`, which exposes tokenizers for OpenAI token sets, and depends on `bpe`.
+- Tests are located in the `tests` subdirectory, and benchmarks in the `benchmarks` subdirectory. Both of these are separate crates so they can depend on `bpe-openai` without causing a cyclic dependency.
+
+Only the `bpe` and `bpe-openai` crates are meant to be published. The other ones are for development use only.
+
+## Running benchmarks
+
+Change the working directory to the `benchmarks` directory:
+
+```sh
+cd benchmarks
+```
+
+Run the benchmark as follows (required [cargo-criterion](https://crates.io/crates/cargo-criterion) installed):
+
+```sh
+cargo criterion
+```
+
+(Using `cargo bench` ignores the settings in `criterion.toml`!)
+Open the full report which should be located in `target/criterion/reports/index.html`.
+
+Update the figures in this repo as follows (requires `rsvg-convert` from `librsvg` installed):
+
+```sh
+script/copy-results
+```
+
+[contributing]: ../../CONTRIBUTING.md

crates/bpe/README.md

@@ -296,26 +296,3 @@ The performance of tiktoken shows a quadratic growth with the input size.
 The Huggingface encoder scales better, but becomes slower and slower compared to our implementation as input size increases.
 
 ![worst-case encoding runtime comparison](./images/performance-worstcase.svg)
-
-### Running the benchmarks
-
-Benchmarks are located in a separate crate in the `benchmarks` directory.
-
-```sh
-cd benchmarks
-```
-
-Run the benchmark as follows (required [cargo-criterion](https://crates.io/crates/cargo-criterion) installed):
-
-```sh
-cargo criterion
-```
-
-(Using `cargo bench` ignores the settings in `criterion.toml`!)
-Open the full report which should be located in `target/criterion/reports/index.html`.
-
-Update the figures in this repo as follows (requires `rsvg-convert` from `librsvg` installed):
-
-```sh
-script/copy-results
-```