+/*
+ * This file is part of the GROMACS molecular simulation package.
+ *
+ * Copyright (c) 2019, 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.
+ *
+ * GROMACS is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2.1
+ * of the License, or (at your option) any later version.
+ *
+ * GROMACS is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with GROMACS; if not, see
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+ */
+
+/*! \internal \file
+ *
+ * \brief Declares constants and helper functions used when handling
+ * bounding boxes for clusters of particles.
+ *
+ * \author Berk Hess <hess@kth.se>
+ * \ingroup module_nbnxm
+ */
+
+#ifndef GMX_NBNXM_BOUNDINGBOXES_H
+#define GMX_NBNXM_BOUNDINGBOXES_H
+
+#include "gromacs/simd/simd.h"
+
+namespace Nbnxm
+{
+
+/*! \brief The number of bounds along one dimension of a bounding box */
+static constexpr int c_numBoundingBoxBounds1D = 2;
+
+} // namespace Nbnxm
+
+#ifndef DOXYGEN
+
+/* Bounding box calculations are (currently) always in single precision, so
+ * we only need to check for single precision support here.
+ * This uses less (cache-)memory and SIMD is faster, at least on x86.
+ */
+#if GMX_SIMD4_HAVE_FLOAT
+# define NBNXN_SEARCH_BB_SIMD4 1
+#else
+# define NBNXN_SEARCH_BB_SIMD4 0
+#endif
+
+
+#if NBNXN_SEARCH_BB_SIMD4
+/* Always use 4-wide SIMD for bounding box calculations */
+
+# if !GMX_DOUBLE
+/* Single precision BBs + coordinates, we can also load coordinates with SIMD */
+# define NBNXN_SEARCH_SIMD4_FLOAT_X_BB 1
+# else
+# define NBNXN_SEARCH_SIMD4_FLOAT_X_BB 0
+# endif
+
+/* Store bounding boxes corners as quadruplets: xxxxyyyyzzzz
+ *
+ * The packed bounding box coordinate stride is always set to 4.
+ * With AVX we could use 8, but that turns out not to be faster.
+ */
+# define NBNXN_BBXXXX 1
+
+//! The number of bounding boxes in a pack, also the size of a pack along one dimension
+static constexpr int c_packedBoundingBoxesDimSize = GMX_SIMD4_WIDTH;
+
+//! Total number of corners (floats) in a pack of bounding boxes
+static constexpr int c_packedBoundingBoxesSize =
+ c_packedBoundingBoxesDimSize*DIM*Nbnxm::c_numBoundingBoxBounds1D;
+
+//! Returns the starting index of the bounding box pack that contains the given cluster
+static constexpr inline int packedBoundingBoxesIndex(int clusterIndex)
+{
+ return (clusterIndex/c_packedBoundingBoxesDimSize)*c_packedBoundingBoxesSize;
+}
+
+#else /* NBNXN_SEARCH_BB_SIMD4 */
+
+# define NBNXN_SEARCH_SIMD4_FLOAT_X_BB 0
+# define NBNXN_BBXXXX 0
+
+#endif /* NBNXN_SEARCH_BB_SIMD4 */
+
+#endif // !DOXYGEN
+
+#endif