Add a note on early return in device buffer operations

Functions that (re)allocate, clear and copy to or from
device buffer have an early return in case of zero operation
size. This is a safety mechnism that allows calling these
functions even if the buffers are not intialized, if the
size of the respective buffer is set to zero. A note is
added to the devicebuffer.h that explains why these early
returns are needed.

diff --git a/src/gromacs/gpu_utils/devicebuffer.h b/src/gromacs/gpu_utils/devicebuffer.h
index a13f0c62625315e7979c71e931e93b00924ea382..d3fc1c97d966230a1eafd426e3049e94fd43b2a2 100644 (file)
--- a/src/gromacs/gpu_utils/devicebuffer.h
+++ b/src/gromacs/gpu_utils/devicebuffer.h
@@ -1,7 +1,7 @@
 /*
  * This file is part of the GROMACS molecular simulation package.
  *
- * Copyright (c) 2018,2019,2020, by the GROMACS development team, led by
+ * Copyright (c) 2018,2019,2020,2021, by the GROMACS development team, led by
  * Mark Abraham, David van der Spoel, Berk Hess, and Erik Lindahl,
  * and including many others, as listed in the AUTHORS file in the
  * top-level source directory and at http://www.gromacs.org.
@@ -36,9 +36,14 @@
 #define GMX_GPU_UTILS_DEVICEBUFFER_H
 
 /*! \libinternal \file
- *  \brief Implements the logic for handling of DeviceBuffer types in OpenCL/CUDA.
+ *  \brief Implements the logic for handling of DeviceBuffer types in OpenCL, CUDA and SYCL.
+ *
  *  Can only be included on GPU build paths.
  *
+ *  Note that most of the buffer operations have an early return, if the requested operation
+ *  size is zero. This allows for calling these functions with zero operation size even when
+ *  the underlying buffers were not properly intialized.
+ *
  *  \author Aleksei Iupinov <a.yupinov@gmail.com>
  *
  *  \inlibraryapi