Cuda quantized mmv bugfix. (#2526)

candle-core/src/quantized/cuda.rs

@@ -321,7 +321,7 @@ fn mul_mat_via_q8_1(
     // Start by quantizing y
     let k_padded = pad(k, MATRIX_ROW_PADDING);
     let y_size_in_bytes =
-        k_padded * y_rows * GgmlDType::Q8_1.type_size() / GgmlDType::Q8_1.block_size();
+        k_padded * y_cols * GgmlDType::Q8_1.type_size() / GgmlDType::Q8_1.block_size();
     let mut y_q8_1 = unsafe { dev.alloc::<u8>(y_size_in_bytes).w()? };
     quantize_q8_1(y, &mut y_q8_1, k, y_cols, dev)?;
 
@@ -707,4 +707,28 @@ mod test {
         assert_eq!(vs[15], 13138824.0);
         Ok(())
     }
+
+    // The following test used to fail under compute-sanitizer until #2526.
+    #[test]
+    fn cuda_mm_q8_1_pad() -> Result<()> {
+        let dev = CudaDevice::new(0)?;
+        let (x_rows, ncols, y_cols) = (4, 16, 2048);
+        let vs: Vec<f32> = (0..ncols * y_cols).map(|v| v as f32 / 256.).collect();
+        let y = dev.htod_sync_copy(&vs).w()?;
+        let mut xs = QCudaStorage::zeros(&dev, ncols * x_rows, GgmlDType::Q4_0)?;
+        xs.quantize(&CudaStorage::wrap_cuda_slice(y.clone(), dev.clone()))?;
+        let cuda_storage = mul_mat_via_q8_1(
+            &xs.data,
+            &y.slice(..),
+            /* dtype */ GgmlDType::Q4_0,
+            /* x_rows */ x_rows,
+            /* x_cols */ ncols,
+            /* y_rows */ ncols,
+            /* y_cols */ y_cols,
+            &dev,
+        )?;
+        let vs = cuda_storage.as_cuda_slice::<f32>()?;
+        let _vs = dev.dtoh_sync_copy(&vs.slice(..)).unwrap();
+        Ok(())
+    }
 }