src/gromacs/utility/gmxomp.h

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