Tweak the basic example to show how to implement sort.

candle-core/examples/basics.rs

@@ -5,13 +5,43 @@ extern crate intel_mkl_src;
 extern crate accelerate_src;
 
 use anyhow::Result;
-use candle_core::{Device, Tensor};
+use candle::{CpuStorage, Device, Layout, Shape, Tensor};
+use candle_core as candle;
+
+struct ArgSort;
+impl candle::CustomOp1 for ArgSort {
+    fn name(&self) -> &'static str {
+        "arg-sort"
+    }
+
+    fn cpu_fwd(
+        &self,
+        storage: &CpuStorage,
+        layout: &Layout,
+    ) -> candle::Result<(CpuStorage, Shape)> {
+        if layout.shape().rank() != 1 {
+            candle::bail!(
+                "input should have a single dimension, got {:?}",
+                layout.shape()
+            )
+        }
+        let slice = storage.as_slice::<f32>()?;
+        let src = match layout.contiguous_offsets() {
+            None => candle::bail!("input has to be contiguous"),
+            Some((o1, o2)) => &slice[o1..o2],
+        };
+        let mut dst = (0..src.len() as u32).collect::<Vec<u32>>();
+        dst.sort_by(|&i, &j| src[i as usize].total_cmp(&src[j as usize]));
+        let storage = candle::WithDType::to_cpu_storage_owned(dst);
+        Ok((storage, layout.shape().clone()))
+    }
+}
 
 fn main() -> Result<()> {
-    let a = Tensor::new(&[[0.0f32, 1.0, 2.0], [3.0, 4.0, 5.0]], &Device::Cpu)?;
-    let b = Tensor::new(&[[88.0f32, 99.0]], &Device::Cpu)?;
-    let new_a = a.slice_scatter(&b, 1, 2)?;
-    assert_eq!(a.to_vec2::<f32>()?, [[0.0, 1.0, 2.0], [3.0, 4.0, 5.0]]);
-    assert_eq!(new_a.to_vec2::<f32>()?, [[0.0, 1.0, 2.0], [3.0, 4.0, 5.0]]);
+    let a = Tensor::new(&[0.0f32, 1.0, 3.0, 2.0, -12.0, 4.0, 3.5], &Device::Cpu)?;
+    let indices = a.apply_op1(ArgSort)?;
+    let a_sorted = a.gather(&indices, 0)?;
+    println!("{indices}");
+    println!("{a_sorted}");
     Ok(())
 }