src/gromacs/nbnxm/constants.h

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  35
  36 #ifndef GMX_NBNXN_CONSTANTS_H
  37 #define GMX_NBNXN_CONSTANTS_H
  38
  39 // Lower limit for square interaction distances in nonbonded kernels.
  40 // For smaller values we will overflow when calculating r^-1 or r^-12, but
  41 // to keep it simple we always apply the limit from the tougher r^-12 condition.
  42 #if GMX_DOUBLE
  43 // Some double precision SIMD architectures use single precision in the first
  44 // step, so although the double precision criterion would allow smaller rsq,
  45 // we need to stay in single precision with some margin for the N-R iterations.
  46 #define NBNXN_MIN_RSQ         1.0e-36
  47 #else
  48 // The worst intermediate value we might evaluate is r^-12, which
  49 // means we should ensure r^2 stays above pow(GMX_FLOAT_MAX,-1.0/6.0)*1.01 (some margin)
  50 #define NBNXN_MIN_RSQ         3.82e-07f  // r > 6.2e-4
  51 #endif
  52
  53
  54 /* The number of clusters in a super-cluster, used for GPU */
  55 #define c_nbnxnGpuNumClusterPerSupercluster  8
  56
  57 /* With GPU kernels we group cluster pairs in 4 to optimize memory usage
  58  * of integers containing 32 bits.
  59  */
  60 #define c_nbnxnGpuJgroupSize (32/c_nbnxnGpuNumClusterPerSupercluster)
  61
  62 #endif