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diff --git a/Source/Utils/ParticleUtils.H b/Source/Utils/ParticleUtils.H
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+/* Copyright 2019-2020 Neil Zaim, Yinjian Zhao
+ *
+ * This file is part of WarpX.
+ *
+ * License: BSD-3-Clause-LBNL
+ */
+#ifndef WARPX_PARTICLE_UTILS_H_
+#define WARPX_PARTICLE_UTILS_H_
+
+#include "Particles/WarpXParticleContainer.H"
+#include <AMReX_DenseBins.H>
+
+namespace ParticleUtils {
+
+    /**
+    * \brief Find the particles and count the particles that are in each cell. More specifically
+    * this function returns an amrex::DenseBins object containing an offset array and a permutation
+    * array which can be used to loop over all the cells in a tile and apply an algorithm to
+    * particles of a given species present in each cell.
+    * Note that this does *not* rearrange particle arrays.
+    *
+    * @param[in] lev the index of the refinement level.
+    * @param[in] mfi the MultiFAB iterator.
+    * @param[in] ptile the particle tile.
+    */
+    amrex::DenseBins<WarpXParticleContainer::ParticleType>
+    findParticlesInEachCell( int const lev, amrex::MFIter const& mfi,
+                             WarpXParticleContainer::ParticleTileType const& ptile);
+}
+
+#endif // WARPX_PARTICLE_UTILS_H_