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 /* Ugly hack because the openmp implementation below hacks into the SIMD
  58  * settings to decide when to use _mm_pause(). This should eventually be
  59  * changed into proper detection of the intrinsics uses, not SIMD.
  60  */
  61 #if GMX_SIMD_X86_SSE2 || GMX_SIMD_X86_SSE4_1 || GMX_SIMD_X86_AVX_128_FMA || \
  62     GMX_SIMD_X86_AVX_256 || GMX_SIMD_X86_AVX2_256
  63 #    include <xmmintrin.h>
  64 #endif
  65 #else
  66 #include <windows.h>
  67 #endif
  68
  69 #include "gromacs/utility/basedefinitions.h"
  70
  71 #ifdef __cplusplus
  72 extern "C"
  73 {
  74 #endif
  75
  76 /*! \addtogroup module_utility
  77  * \{
  78  */
  79
  80 /*! \brief
  81  * Returns an integer equal to or greater than the number of threads
  82  * that would be available if a parallel region without num_threads were
  83  * defined at that point in the code.
  84  *
  85  * Acts as a wrapper for omp_get_max_threads().
  86  */
  87 int gmx_omp_get_max_threads(void);
  88
  89 /*! \brief
  90  * Returns the number of processors available when the function is called.
  91  *
  92  * Acts as a wrapper around omp_get_num_procs().
  93  */
  94 int gmx_omp_get_num_procs(void);
  95
  96 /*! \brief
  97  * Returns the thread number of the thread executing within its thread team.
  98  *
  99  * Acts as a wrapper for omp_get_thread_num().
 100  */
 101 int gmx_omp_get_thread_num(void);
 102
 103 /*! \brief
 104  * Sets the number of threads in subsequent parallel regions, unless overridden
 105  * by a num_threads clause.
 106  *
 107  * Acts as a wrapper for omp_set_num_threads().
 108  */
 109 void gmx_omp_set_num_threads(int num_threads);
 110
 111 /*! \brief
 112  * Check for externally set thread affinity to avoid conflicts with \Gromacs
 113  * internal setting.
 114  *
 115  * \param[out] message  Receives the message to be shown to the user.
 116  * \returns `true` if we can set thread affinity ourselves.
 117  *
 118  * The KMP_AFFINITY environment variable is used by Intel, GOMP_CPU_AFFINITY
 119  * by the GNU compilers (Intel also honors it well).  If any of the variables
 120  * is set, we should honor it and disable the internal pinning.
 121  *
 122  * If this function returns `false`, the caller is responsible to disable the
 123  * pinning, show the message from \p *message to the user, and free the memory
 124  * allocated for \p *message.
 125  * If the return value is `true`, \p *message is NULL.
 126  */
 127 gmx_bool gmx_omp_check_thread_affinity(char **message);
 128
 129 /*! \brief
 130  * Pause for use in a spin-wait loop.
 131  */
 132 static gmx_inline void gmx_pause()
 133 {
 134 #ifndef _MSC_VER
 135     /* Ugly hack because the openmp implementation below hacks into the SIMD
 136      * settings to decide when to use _mm_pause(). This should eventually be
 137      * changed into proper detection of the intrinsics uses, not SIMD.
 138      */
 139 #if (GMX_SIMD_X86_SSE2 || GMX_SIMD_X86_SSE4_1 || GMX_SIMD_X86_AVX_128_FMA || \
 140      GMX_SIMD_X86_AVX_256 || GMX_SIMD_X86_AVX2_256) && !defined(__MINGW32__)
 141     /* Replace with tbb::internal::atomic_backoff when/if we use TBB */
 142     _mm_pause();
 143 #elif defined __MIC__
 144     _mm_delay_32(32);
 145 #else
 146     /* No wait for unknown architecture */
 147 #endif
 148 #else
 149     YieldProcessor();
 150 #endif
 151 }
 152
 153 /*! \} */
 154
 155 #ifdef __cplusplus
 156 }
 157 #endif
 158
 159 #endif