src/gromacs/utility/gmxomp.h

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  35 /*! \libinternal \file
  36  * \brief
  37  * Declares OpenMP wrappers to avoid conditional compilation.
  38  *
  39  * This module defines wrappers for OpenMP API functions and enables compiling
  40  * code without conditional compilation even when OpenMP is turned off in the
  41  * build system.
  42  * Therefore, OpenMP API functions should always be used through these wrappers
  43  * and omp.h should never be directly included.  Instead, this header should be
  44  * used whenever OpenMP API functions are needed.
  45  *
  46  * \inlibraryapi
  47  * \ingroup module_utility
  48  */
  49 #ifndef GMX_UTILITY_OMP_H
  50 #define GMX_UTILITY_OMP_H
  51
  52 #include "config.h"
  53
  54 #include <stdio.h>
  55
  56 #if GMX_NATIVE_WINDOWS
  57 #include <windows.h>
  58 #elif HAVE_XMMINTRIN_H
  59 #include <xmmintrin.h>
  60 #endif
  61
  62 #include "gromacs/utility/basedefinitions.h"
  63
  64 /*! \addtogroup module_utility
  65  * \{
  66  */
  67
  68 /*! \brief
  69  * Returns an integer equal to or greater than the number of threads
  70  * that would be available if a parallel region without num_threads were
  71  * defined at that point in the code.
  72  *
  73  * Acts as a wrapper for omp_get_max_threads().
  74  */
  75 int gmx_omp_get_max_threads();
  76
  77 /*! \brief
  78  * Returns the number of processors available when the function is called.
  79  *
  80  * Acts as a wrapper around omp_get_num_procs().
  81  */
  82 int gmx_omp_get_num_procs();
  83
  84 /*! \brief
  85  * Returns the thread number of the thread executing within its thread team.
  86  *
  87  * Acts as a wrapper for omp_get_thread_num().
  88  */
  89 int gmx_omp_get_thread_num();
  90
  91 /*! \brief
  92  * Sets the number of threads in subsequent parallel regions, unless overridden
  93  * by a num_threads clause.
  94  *
  95  * Acts as a wrapper for omp_set_num_threads().
  96  */
  97 void gmx_omp_set_num_threads(int num_threads);
  98
  99 /*! \brief
 100  * Check for externally set thread affinity to avoid conflicts with \Gromacs
 101  * internal setting.
 102  *
 103  * \param[out] message  Receives the message to be shown to the user.
 104  * \returns `true` if we can set thread affinity ourselves.
 105  *
 106  * The KMP_AFFINITY environment variable is used by Intel, GOMP_CPU_AFFINITY
 107  * by the GNU compilers (Intel also honors it well).  If any of the variables
 108  * is set, we should honor it and disable the internal pinning.
 109  *
 110  * If this function returns `false`, the caller is responsible to disable the
 111  * pinning, show the message from \p *message to the user, and free the memory
 112  * allocated for \p *message.
 113  * If the return value is `true`, \p *message is NULL.
 114  */
 115 gmx_bool gmx_omp_check_thread_affinity(char **message);
 116
 117 /*! \brief
 118  * Pause for use in a spin-wait loop.
 119  */
 120 static inline void gmx_pause()
 121 {
 122 #if GMX_NATIVE_WINDOWS
 123     YieldProcessor();
 124 #elif HAVE_XMMINTRIN_H
 125     _mm_pause();
 126 #elif defined __MIC__
 127     _mm_delay_32(32);
 128 #else
 129     // No wait for unknown architecture
 130 #endif
 131 }
 132
 133 /*! \} */
 134
 135 #endif