feat(gpu): add a function to set a CudaLweList to 0

tfhe/src/core_crypto/gpu/entities/lwe_ciphertext_list.rs

@@ -220,4 +220,19 @@ impl<T: UnsignedInteger> CudaLweCiphertextList<T> {
     pub(crate) fn ciphertext_modulus(&self) -> CiphertextModulus<T> {
         self.0.ciphertext_modulus
     }
+
+    /// # Safety
+    ///
+    /// - `stream` __must__ be synchronized to guarantee computation has finished, and inputs must
+    ///   not be dropped until stream is synchronised
+    pub unsafe fn set_to_zero_async(&mut self, streams: &CudaStreams) {
+        self.0.d_vec.memset_async(0u64, streams, 0);
+    }
+
+    pub fn set_to_zero(&mut self, streams: &CudaStreams) {
+        unsafe {
+            self.set_to_zero_async(streams);
+            streams.synchronize_one(0);
+        }
+    }
 }

tfhe/src/core_crypto/gpu/vec.rs

@@ -175,16 +175,13 @@ impl<T: Numeric> CudaVec<T> {
     ///
     /// - `streams` __must__ be synchronized to guarantee computation has finished, and inputs must
     ///   not be dropped until streams is synchronised
-    pub unsafe fn memset_async(&mut self, value: T, streams: &CudaStreams, stream_index: u32)
-    where
-        T: Into<u64>,
-    {
+    pub unsafe fn memset_async(&mut self, value: u64, streams: &CudaStreams, stream_index: u32) {
         let size = self.len() * std::mem::size_of::<T>();
         // We check that self is not empty to avoid invalid pointers
         if size > 0 {
             cuda_memset_async(
                 self.as_mut_c_ptr(stream_index),
-                value.into(),
+                value,
                 size as u64,
                 streams.ptr[stream_index as usize],
                 streams.gpu_indexes[stream_index as usize].0,