src/gromacs/nbnxm/nbnxm_geometry.cpp

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  35
  36 #include "gmxpre.h"
  37
  38 #include "nbnxm_geometry.h"
  39
  40 #include "gromacs/nbnxm/nbnxm.h"
  41 #include "gromacs/nbnxm/pairlist.h"
  42 #include "gromacs/utility/fatalerror.h"
  43 #include "gromacs/utility/real.h"
  44
  45 /* Clusters at the cut-off only increase rlist by 60% of their size */
  46 static constexpr real c_nbnxnRlistIncreaseOutsideFactor = 0.6;
  47
  48 real nbnxn_get_rlist_effective_inc(const int  jClusterSize,
  49                                    const real atomDensity)
  50 {
  51     /* We should get this from the setup, but currently it's the same for
  52      * all setups, including GPUs.
  53      */
  54     const real iClusterSize    = c_nbnxnCpuIClusterSize;
  55
  56     const real iVolumeIncrease = (iClusterSize - 1)/atomDensity;
  57     const real jVolumeIncrease = (jClusterSize - 1)/atomDensity;
  58
  59     return c_nbnxnRlistIncreaseOutsideFactor*std::cbrt(iVolumeIncrease +
  60                                                        jVolumeIncrease);
  61 }
  62
  63 real nbnxn_get_rlist_effective_inc(const int        clusterSize,
  64                                    const gmx::RVec &averageClusterBoundingBox)
  65 {
  66     /* The average length of the diagonal of a sub cell */
  67     const real diagonal    = std::sqrt(norm2(averageClusterBoundingBox));
  68
  69     const real volumeRatio = (clusterSize - 1.0_real)/clusterSize;
  70
  71     return c_nbnxnRlistIncreaseOutsideFactor*gmx::square(volumeRatio)*0.5_real*diagonal;
  72 }