Add more conv2d support. (#340)

* Add more conv2d support.

* Conv2d cpu work.

* Conv2d output shape.

candle-core/src/tensor.rs

@@ -817,8 +817,34 @@ impl Tensor {
         Ok(from_storage(storage, out_dims, op, false))
     }
 
-    pub fn conv2d(&self, _kernel: &Self, _padding: usize, _stride: usize) -> Result<Self> {
-        todo!()
+    pub fn conv2d(&self, kernel: &Self, padding: usize, stride: usize) -> Result<Self> {
+        let (b_size, c_in, i_h, i_w) = self.dims4()?;
+        let (c_out, c_in_k, k_h, k_w) = kernel.dims4()?;
+        if c_in != c_in_k {
+            crate::bail!("in_channel mismatch between input ({c_in}) and kernel ({c_in_k})")
+        }
+        let params = crate::conv::ParamsConv2D {
+            b_size,
+            i_h,
+            i_w,
+            k_h,
+            k_w,
+            c_out,
+            c_in,
+            padding,
+            stride,
+        };
+        let storage =
+            self.storage()
+                .conv2d(self.layout(), &kernel.storage(), kernel.layout(), &params)?;
+        let op = BackpropOp::new2(self, kernel, |arg, kernel| Op::Conv2D {
+            arg,
+            kernel,
+            padding,
+            stride,
+        });
+        let out_dims = params.out_dims();
+        Ok(from_storage(storage, out_dims, op, false))
     }
 
     pub fn upsample_nearest2d(&self, target_h: usize, target_w: usize) -> Result<Self> {