src/gromacs/simd/support.cpp

   1 /*
   2  * This file is part of the GROMACS molecular simulation package.
   3  *
   4  * Copyright (c) 2015,2016,2017,2018, by the GROMACS development team, led by
   5  * Mark Abraham, David van der Spoel, Berk Hess, and Erik Lindahl,
   6  * and including many others, as listed in the AUTHORS file in the
   7  * top-level source directory and at http://www.gromacs.org.
   8  *
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  11  * as published by the Free Software Foundation; either version 2.1
  12  * of the License, or (at your option) any later version.
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  35
  36 /*! \internal \file
  37  *
  38  * \brief Implements SIMD architecture support query routines
  39  *
  40  * \author Erik Lindahl <erik.lindahl@scilifelab.se>
  41  *
  42  * \ingroup module_simd
  43  */
  44
  45 #include "gmxpre.h"
  46
  47 #include "support.h"
  48
  49 #include "config.h"
  50
  51 #include <cstdio>
  52 #include <cstdlib>
  53
  54 #include <map>
  55 #include <string>
  56
  57 #include "gromacs/hardware/cpuinfo.h"
  58 #include "gromacs/hardware/identifyavx512fmaunits.h"
  59 #include "gromacs/utility/stringutil.h"
  60
  61 namespace gmx
  62 {
  63
  64 /*! \cond libapi */
  65
  66 const std::string &
  67 simdString(SimdType s)
  68 {
  69     static const std::map<SimdType, std::string> name =
  70     {
  71         { SimdType::None,           "None"            },
  72         { SimdType::Reference,      "Reference"       },
  73         { SimdType::Generic,        "Generic"         },
  74         { SimdType::X86_Sse2,       "SSE2"            },
  75         { SimdType::X86_Sse4_1,     "SSE4.1"          },
  76         { SimdType::X86_Avx128Fma,  "AVX_128_FMA"     },
  77         { SimdType::X86_Avx,        "AVX_256"         },
  78         { SimdType::X86_Avx2,       "AVX2_256"        },
  79         { SimdType::X86_Avx2_128,   "AVX2_128"        },
  80         { SimdType::X86_Avx512,     "AVX_512"         },
  81         { SimdType::X86_Avx512Knl,  "AVX_512_KNL"     },
  82         { SimdType::X86_Mic,        "X86_MIC"         },
  83         { SimdType::Arm_Neon,       "ARM_NEON"        },
  84         { SimdType::Arm_NeonAsimd,  "ARM_NEON_ASIMD"  },
  85         { SimdType::Ibm_Vmx,        "IBM_VMX"         },
  86         { SimdType::Ibm_Vsx,        "IBM_VSX"         },
  87         { SimdType::Fujitsu_HpcAce, "Fujitsu HPC-ACE" }
  88     };
  89
  90     return name.at(s);
  91 }
  92
  93 SimdType
  94 simdSuggested(const CpuInfo &c)
  95 {
  96     SimdType suggested = SimdType::None;
  97
  98     if (c.supportLevel() >= CpuInfo::SupportLevel::Features)
  99     {
 100         switch (c.vendor())
 101         {
 102             case CpuInfo::Vendor::Intel:
 103                 if (c.feature(CpuInfo::Feature::X86_Avx512ER))
 104                 {
 105                     suggested = SimdType::X86_Avx512Knl;
 106                 }
 107                 else if (c.feature(CpuInfo::Feature::X86_Avx512F))
 108                 {
 109                     // If we could not identify the number of AVX512 FMA units we assume 2
 110                     suggested = ( identifyAvx512FmaUnits() == 1 ) ? SimdType::X86_Avx2 : SimdType::X86_Avx512;
 111                 }
 112                 else if (c.feature(CpuInfo::Feature::X86_Avx2))
 113                 {
 114                     suggested = SimdType::X86_Avx2;
 115                 }
 116                 else if (c.feature(CpuInfo::Feature::X86_Avx))
 117                 {
 118                     suggested = SimdType::X86_Avx;
 119                 }
 120                 else if (c.feature(CpuInfo::Feature::X86_Sse4_1))
 121                 {
 122                     suggested = SimdType::X86_Sse4_1;
 123                 }
 124                 else if (c.feature(CpuInfo::Feature::X86_Sse2))
 125                 {
 126                     suggested = SimdType::X86_Sse2;
 127                 }
 128                 break;
 129             case CpuInfo::Vendor::Amd:
 130                 if (c.feature(CpuInfo::Feature::X86_Avx2))
 131                 {
 132                     // AMD Ryzen supports 256-bit AVX2, but performs better with 128-bit
 133                     // since it can execute two independent such instructions per cycle,
 134                     // and wider SIMD has slightly lower efficiency in GROMACS.
 135                     suggested = SimdType::X86_Avx2_128;
 136                 }
 137                 else if (c.feature(CpuInfo::Feature::X86_Avx))
 138                 {
 139                     // Use 128-bit FMA SIMD if Fma4 flag is set, otherwise plain 256-bit AVX
 140                     if (c.feature(CpuInfo::Feature::X86_Fma4))
 141                     {
 142                         suggested = SimdType::X86_Avx128Fma;
 143                     }
 144                     else
 145                     {
 146                         suggested = SimdType::X86_Avx;
 147                     }
 148                 }
 149                 else if (c.feature(CpuInfo::Feature::X86_Sse4_1))
 150                 {
 151                     suggested = SimdType::X86_Sse4_1;
 152                 }
 153                 else if (c.feature(CpuInfo::Feature::X86_Sse2))
 154                 {
 155                     suggested = SimdType::X86_Sse2;
 156                 }
 157
 158                 break;
 159             case CpuInfo::Vendor::Arm:
 160                 if (c.feature(CpuInfo::Feature::Arm_NeonAsimd))
 161                 {
 162                     suggested = SimdType::Arm_NeonAsimd;
 163                 }
 164                 else if (c.feature(CpuInfo::Feature::Arm_Neon))
 165                 {
 166                     suggested = SimdType::Arm_Neon;
 167                 }
 168                 break;
 169             case CpuInfo::Vendor::Ibm:
 170                 if (c.feature(CpuInfo::Feature::Ibm_Vsx))
 171                 {
 172                     suggested = SimdType::Ibm_Vsx;
 173                 }
 174                 else if (c.feature(CpuInfo::Feature::Ibm_Vmx))
 175                 {
 176                     suggested = SimdType::Ibm_Vmx;
 177                 }
 178                 break;
 179             case CpuInfo::Vendor::Fujitsu:
 180                 if (c.feature(CpuInfo::Feature::Fujitsu_HpcAce))
 181                 {
 182                     suggested = SimdType::Fujitsu_HpcAce;
 183                 }
 184                 break;
 185             default:
 186                 break;
 187         }
 188     }
 189     return suggested;
 190 }
 191
 192 SimdType
 193 simdCompiled()
 194 {
 195 #if GMX_SIMD_X86_AVX_512_KNL
 196     return SimdType::X86_Avx512Knl;
 197 #elif GMX_SIMD_X86_AVX_512
 198     return SimdType::X86_Avx512;
 199 #elif GMX_SIMD_X86_MIC
 200     return SimdType::X86_Mic;
 201 #elif GMX_SIMD_X86_AVX2_256
 202     return SimdType::X86_Avx2;
 203 #elif GMX_SIMD_X86_AVX2_128
 204     return SimdType::X86_Avx2_128;
 205 #elif GMX_SIMD_X86_AVX_256
 206     return SimdType::X86_Avx;
 207 #elif GMX_SIMD_X86_AVX_128_FMA
 208     return SimdType::X86_Avx128Fma;
 209 #elif GMX_SIMD_X86_SSE4_1
 210     return SimdType::X86_Sse4_1;
 211 #elif GMX_SIMD_X86_SSE2
 212     return SimdType::X86_Sse2;
 213 #elif GMX_SIMD_ARM_NEON
 214     return SimdType::Arm_Neon;
 215 #elif GMX_SIMD_ARM_NEON_ASIMD
 216     return SimdType::Arm_NeonAsimd;
 217 #elif GMX_SIMD_IBM_VMX
 218     return SimdType::Ibm_Vmx;
 219 #elif GMX_SIMD_IBM_VSX
 220     return SimdType::Ibm_Vsx;
 221 #elif GMX_SIMD_SPARC64_HPC_ACE
 222     return SimdType::Fujitsu_HpcAce;
 223 #elif GMX_SIMD_REFERENCE
 224     return SimdType::Reference;
 225 #else
 226     return SimdType::None;
 227 #endif
 228 }
 229
 230 bool
 231 simdCheck(gmx::SimdType    wanted,
 232           FILE *           log,
 233           bool             warnToStdErr)
 234 {
 235     SimdType             compiled  = simdCompiled();
 236
 237     gmx::TextLineWrapper wrapper;
 238     std::string          logMsg;
 239     std::string          warnMsg;
 240
 241     wrapper.settings().setLineLength(78);
 242
 243     if (compiled == SimdType::X86_Avx2 && wanted == SimdType::X86_Avx512)
 244     {
 245         logMsg = wrapper.wrapToString(formatString("Highest SIMD level requested by all nodes in run: %s\n"
 246                                                    "SIMD instructions selected at compile time:       %s\n"
 247                                                    "This program was compiled for different hardware than you are running on, "
 248                                                    "which could influence performance. This build might have been configured on "
 249                                                    "a login node with only a single AVX-512 FMA unit (in which case AVX2 is faster), "
 250                                                    "while the node you are running on has dual AVX-512 FMA units.",
 251                                                    simdString(wanted).c_str(), simdString(compiled).c_str()));
 252         warnMsg = wrapper.wrapToString(formatString("Compiled SIMD: %s, but for this host/run %s might be better (see log).",
 253                                                     simdString(compiled).c_str(), simdString(wanted).c_str()));
 254     }
 255     else if (compiled == SimdType::X86_Avx512 && wanted == SimdType::X86_Avx2 && identifyAvx512FmaUnits() == 1)
 256     {
 257         // The reason for explicitly checking the number of FMA units above is to avoid triggering
 258         // this conditional if the AVX2 SIMD was requested by some other node in a heterogeneous MPI run.
 259         logMsg = wrapper.wrapToString(formatString("Highest SIMD level requested by all nodes in run: %s\n"
 260                                                    "SIMD instructions selected at compile time:       %s\n"
 261                                                    "This program was compiled for different hardware than you are running on, "
 262                                                    "which could influence performance."
 263                                                    "This host supports AVX-512, but since it only has 1 AVX-512"
 264                                                    "FMA unit, it would be faster to use AVX2 instead.",
 265                                                    simdString(wanted).c_str(), simdString(compiled).c_str()));
 266         warnMsg = wrapper.wrapToString(formatString("Compiled SIMD: %s, but for this host/run %s might be better (see log).",
 267                                                     simdString(compiled).c_str(), simdString(wanted).c_str()));
 268     }
 269     else if (compiled == SimdType::X86_Avx2 && wanted == SimdType::X86_Avx2_128)
 270     {
 271         // Wanted SimdType::X86_Avx2_128 can only be the AMD Zen architecture.
 272         // AVX2_256 is only up to a few percent slower than AVX2_128
 273         // in both single and double precision. AVX2_256 is slightly
 274         // faster with nonbondeds and PME on a GPU. Don't warn the user.
 275     }
 276     else if (compiled > wanted && !(compiled == SimdType::X86_Avx && wanted == SimdType::X86_Avx128Fma))
 277     {
 278         // Normally it is close to catastrophic if the compiled SIMD type is larger than
 279         // the supported one, but AVX128Fma is an exception: AMD CPUs will (strongly) prefer
 280         // AVX128Fma, but they will work fine with AVX too. Thus, make an exception for this.
 281         logMsg = wrapper.wrapToString(formatString("Highest SIMD level requested by all nodes in run: %s\n"
 282                                                    "SIMD instructions selected at compile time:       %s\n"
 283                                                    "Compiled SIMD newer than requested; program might crash.",
 284                                                    simdString(wanted).c_str(), simdString(compiled).c_str()));
 285         warnMsg = logMsg;
 286     }
 287     else if (wanted != compiled)
 288     {
 289         // This warning will also occur if compiled is X86_Avx and wanted is X86_Avx128Fma
 290         logMsg = wrapper.wrapToString(formatString("Highest SIMD level requested by all nodes in run: %s\n"
 291                                                    "SIMD instructions selected at compile time:       %s\n"
 292                                                    "This program was compiled for different hardware than you are running on, "
 293                                                    "which could influence performance.",
 294                                                    simdString(wanted).c_str(), simdString(compiled).c_str()));
 295         warnMsg = wrapper.wrapToString(formatString("Compiled SIMD: %s, but for this host/run %s might be better (see log).",
 296                                                     simdString(compiled).c_str(), simdString(wanted).c_str()));
 297     }
 298
 299     if (!logMsg.empty() && log != nullptr)
 300     {
 301         fprintf(log, "%s\n", logMsg.c_str());
 302     }
 303     if (!warnMsg.empty() && warnToStdErr)
 304     {
 305         fprintf(stderr, "%s\n", warnMsg.c_str());
 306     }
 307
 308     return (wanted == compiled);
 309 }
 310
 311 /*! \endcond */
 312
 313 }  // namespace gmx