add example to README

README.md

@@ -106,6 +106,67 @@ cuvsCagraIndexParamsDestroy(index_params);
 cuvsResourcesDestroy(res);
 ```
 
+### Rust API
+
+```rust
+use cuvs::cagra::{Index, IndexParams, SearchParams};
+use cuvs::{ManagedTensor, Resources, Result};
+
+use ndarray::s;
+use ndarray_rand::rand_distr::Uniform;
+use ndarray_rand::RandomExt;
+
+/// Example showing how to index and search data with CAGRA
+fn cagra_example() -> Result<()> {
+    let res = Resources::new()?;
+
+    // Create a new random dataset to index
+    let n_datapoints = 65536;
+    let n_features = 512;
+    let dataset =
+        ndarray::Array::<f32, _>::random((n_datapoints, n_features), Uniform::new(0., 1.0));
+
+    // build the cagra index
+    let build_params = IndexParams::new()?;
+    let index = Index::build(&res, &build_params, &dataset)?;
+    println!(
+        "Indexed {}x{} datapoints into cagra index",
+        n_datapoints, n_features
+    );
+
+    // use the first 4 points from the dataset as queries : will test that we get them back
+    // as their own nearest neighbor
+    let n_queries = 4;
+    let queries = dataset.slice(s![0..n_queries, ..]);
+
+    let k = 10;
+
+    // CAGRA search API requires queries and outputs to be on device memory
+    // copy query data over, and allocate new device memory for the distances/ neighbors
+    // outputs
+    let queries = ManagedTensor::from(&queries).to_device(&res)?;
+    let mut neighbors_host = ndarray::Array::<u32, _>::zeros((n_queries, k));
+    let neighbors = ManagedTensor::from(&neighbors_host).to_device(&res)?;
+
+    let mut distances_host = ndarray::Array::<f32, _>::zeros((n_queries, k));
+    let distances = ManagedTensor::from(&distances_host).to_device(&res)?;
+
+    let search_params = SearchParams::new()?;
+
+    index.search(&res, &search_params, &queries, &neighbors, &distances)?;
+
+    // Copy back to host memory
+    distances.to_host(&res, &mut distances_host)?;
+    neighbors.to_host(&res, &mut neighbors_host)?;
+
+    // nearest neighbors should be themselves, since queries are from the
+    // dataset
+    println!("Neighbors {:?}", neighbors_host);
+    println!("Distances {:?}", distances_host);
+    Ok(())
+}
+```
+
 
 ## Contributing