add as_cuda_slice_mut to CudaStorage and CudaDType (#2859)

Author: zackangelo

candle-core/benches/benchmarks/mod.rs

@@ -21,7 +21,9 @@ impl BenchDevice for Device {
             Device::Cpu => Ok(()),
             Device::Cuda(device) => {
                 #[cfg(feature = "cuda")]
-                return Ok(device.synchronize()?);
+                return Ok(device
+                    .synchronize()
+                    .map_err(|e| candle_core::Error::Cuda(Box::new(e)))?);
                 #[cfg(not(feature = "cuda"))]
                 panic!("Cuda device without cuda feature enabled: {:?}", device)
             }

candle-core/src/cuda_backend/mod.rs

@@ -1001,6 +1001,7 @@ pub struct CudaStorage {
 
 pub trait CudaDType: Sized {
     fn as_cuda_slice(s: &CudaStorage) -> Result<&CudaSlice<Self>>;
+    fn as_cuda_slice_mut(s: &mut CudaStorage) -> Result<&mut CudaSlice<Self>>;
     fn wrap_cuda_slice(s: CudaSlice<Self>, dev: CudaDevice) -> CudaStorage;
 }
 
@@ -1019,6 +1020,18 @@ macro_rules! cuda_dtype {
                 }
             }
 
+            fn as_cuda_slice_mut(s: &mut CudaStorage) -> Result<&mut CudaSlice<Self>> {
+                match s.slice {
+                    CudaStorageSlice::$dtype(ref mut data) => Ok(data),
+                    _ => Err(crate::Error::UnexpectedDType {
+                        expected: DType::$dtype,
+                        got: s.dtype(),
+                        msg: "unexpected dtype",
+                    }
+                    .bt()),
+                }
+            }
+
             fn wrap_cuda_slice(slice: CudaSlice<Self>, device: CudaDevice) -> CudaStorage {
                 let slice = CudaStorageSlice::$dtype(slice);
                 CudaStorage { slice, device }
@@ -1042,6 +1055,10 @@ impl CudaStorage {
     pub fn as_cuda_slice<T: CudaDType>(&self) -> Result<&CudaSlice<T>> {
         T::as_cuda_slice(self)
     }
+
+    pub fn as_cuda_slice_mut<T: CudaDType>(&mut self) -> Result<&mut CudaSlice<T>> {
+        T::as_cuda_slice_mut(self)
+    }
 }
 
 fn gemm_config<T>(