src/gromacs/mdlib/nbnxn_consts.h

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  35
  36 #ifndef _nbnxn_consts_h
  37 #define _nbnxn_consts_h
  38
  39 #ifdef __cplusplus
  40 extern "C" {
  41 #endif
  42
  43
  44 /* With CPU kernels the i-cluster size is always 4 atoms.
  45  * With x86 SIMD the j-cluster size can be 2, 4 or 8, otherwise 4.
  46  */
  47 #define NBNXN_CPU_CLUSTER_I_SIZE       4
  48
  49 #define NBNXN_CPU_CLUSTER_I_SIZE_2LOG  2
  50
  51 // Lower limit for square interaction distances in nonbonded kernels.
  52 // For smaller values we will overflow when calculating r^-1 or r^-12, but
  53 // to keep it simple we always apply the limit from the tougher r^-12 condition.
  54 #if GMX_DOUBLE
  55 // Some double precision SIMD architectures use single precision in the first
  56 // step, so although the double precision criterion would allow smaller rsq,
  57 // we need to stay in single precision with some margin for the N-R iterations.
  58 #define NBNXN_MIN_RSQ         1.0e-36
  59 #else
  60 // The worst intermediate value we might evaluate is r^-12, which
  61 // means we should ensure r^2 stays above pow(GMX_FLOAT_MAX,-1.0/6.0)*1.01 (some margin)
  62 #define NBNXN_MIN_RSQ         3.82e-07f  // r > 6.2e-4
  63 #endif
  64
  65
  66 /* Cluster-pair Interaction masks for 4xN and 2xNN kernels.
  67  * Bit i*CJ_SIZE + j tells if atom i and j interact.
  68  */
  69 /* All interaction mask is the same for all kernels */
  70 #define NBNXN_INTERACTION_MASK_ALL        0xffffffffU
  71 /* 4x4 kernel diagonal mask */
  72 #define NBNXN_INTERACTION_MASK_DIAG       0x08ceU
  73 /* 4x2 kernel diagonal masks */
  74 #define NBNXN_INTERACTION_MASK_DIAG_J2_0  0x0002U
  75 #define NBNXN_INTERACTION_MASK_DIAG_J2_1  0x002fU
  76 /* 4x8 kernel diagonal masks */
  77 #define NBNXN_INTERACTION_MASK_DIAG_J8_0  0xf0f8fcfeU
  78 #define NBNXN_INTERACTION_MASK_DIAG_J8_1  0x0080c0e0U
  79
  80
  81 #ifdef __cplusplus
  82 }
  83 #endif
  84
  85 #endif