Tpetra_Details_Behavior.cpp

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// @HEADER
// *****************************************************************************
//          Tpetra: Templated Linear Algebra Services Package
//
// Copyright 2008 NTESS and the Tpetra contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER
 
// clang-format on
#include <algorithm> // std::transform
#include <array>
#include <cctype>  // std::toupper
#include <cstdlib> // std::getenv
#include <functional>
#include <map>
#include <stdexcept>
#include <string>
#include <string_view>
#include <vector>
 
#include "Teuchos_OrdinalTraits.hpp"
#include "Teuchos_TestForException.hpp"
#include "TpetraCore_config.h"
#include "Tpetra_Details_Behavior.hpp"
#include "KokkosKernels_config.h"  // for TPL enable macros
 
// environ should be available on posix platforms
#if not(defined(WIN) && (_MSC_VER >= 1900))
// needs to be in the global namespace
extern char **environ;
#endif
 
namespace Tpetra {
namespace Details {
 
namespace BehaviorDetails {
 
constexpr const std::string_view RESERVED_PREFIX = "TPETRA_";
constexpr const std::string_view ASSUME_GPU_AWARE_MPI =
    "TPETRA_ASSUME_GPU_AWARE_MPI";
constexpr const std::string_view CUDA_LAUNCH_BLOCKING = "CUDA_LAUNCH_BLOCKING";
constexpr const std::string_view MM_TAFC_OptimizationCoreCount =
    "MM_TAFC_OptimizationCoreCount";
constexpr const std::string_view VERBOSE_PRINT_COUNT_THRESHOLD =
    "TPETRA_VERBOSE_PRINT_COUNT_THRESHOLD";
constexpr const std::string_view ROW_IMBALANCE_THRESHOLD =
    "TPETRA_ROW_IMBALANCE_THRESHOLD";
constexpr const std::string_view MULTIVECTOR_USE_MERGE_PATH =
    "TPETRA_MULTIVECTOR_USE_MERGE_PATH";
constexpr const std::string_view VECTOR_DEVICE_THRESHOLD =
    "TPETRA_VECTOR_DEVICE_THRESHOLD";
constexpr const std::string_view HIERARCHICAL_UNPACK_BATCH_SIZE =
    "TPETRA_HIERARCHICAL_UNPACK_BATCH_SIZE";
constexpr const std::string_view HIERARCHICAL_UNPACK_TEAM_SIZE =
    "TPETRA_HIERARCHICAL_UNPACK_TEAM_SIZE";
constexpr const std::string_view USE_TEUCHOS_TIMERS =
    "TPETRA_USE_TEUCHOS_TIMERS";
constexpr const std::string_view USE_KOKKOS_PROFILING =
    "TPETRA_USE_KOKKOS_PROFILING";
constexpr const std::string_view DEBUG = "TPETRA_DEBUG";
constexpr const std::string_view VERBOSE = "TPETRA_VERBOSE";
constexpr const std::string_view TIMING = "TPETRA_TIMING";
constexpr const std::string_view HIERARCHICAL_UNPACK =
    "TPETRA_HIERARCHICAL_UNPACK";
constexpr const std::string_view SKIP_COPY_AND_PERMUTE =
    "TPETRA_SKIP_COPY_AND_PERMUTE";
constexpr const std::string_view FUSED_RESIDUAL = "TPETRA_FUSED_RESIDUAL";
constexpr const std::string_view OVERLAP = "TPETRA_OVERLAP";
constexpr const std::string_view SPACES_ID_WARN_LIMIT =
    "TPETRA_SPACES_ID_WARN_LIMIT";
constexpr const std::string_view TIME_KOKKOS_DEEP_COPY =
    "TPETRA_TIME_KOKKOS_DEEP_COPY";
constexpr const std::string_view TIME_KOKKOS_DEEP_COPY_VERBOSE1 =
    "TPETRA_TIME_KOKKOS_DEEP_COPY_VERBOSE1";
constexpr const std::string_view TIME_KOKKOS_DEEP_COPY_VERBOSE2 =
    "TPETRA_TIME_KOKKOS_DEEP_COPY_VERBOSE2";
constexpr const std::string_view TIME_KOKKOS_FENCE = "TPETRA_TIME_KOKKOS_FENCE";
constexpr const std::string_view TIME_KOKKOS_FUNCTIONS =
    "TPETRA_TIME_KOKKOS_FUNCTIONS";
 
// construct an std::array of string_view with any number of provided
// string_views
template <typename... Elems>
constexpr std::array<std::string_view, sizeof...(Elems)>
make_array(Elems &&... elems) {
  return {std::forward<Elems>(elems)...};
}
 
constexpr const auto RECOGNIZED_VARS = make_array(
    ASSUME_GPU_AWARE_MPI, CUDA_LAUNCH_BLOCKING, MM_TAFC_OptimizationCoreCount,
    VERBOSE_PRINT_COUNT_THRESHOLD, ROW_IMBALANCE_THRESHOLD,
    MULTIVECTOR_USE_MERGE_PATH, VECTOR_DEVICE_THRESHOLD,
    HIERARCHICAL_UNPACK_BATCH_SIZE, HIERARCHICAL_UNPACK_TEAM_SIZE,
    USE_TEUCHOS_TIMERS, USE_KOKKOS_PROFILING, DEBUG, VERBOSE, TIMING,
    HIERARCHICAL_UNPACK, SKIP_COPY_AND_PERMUTE, FUSED_RESIDUAL, OVERLAP,
    SPACES_ID_WARN_LIMIT, TIME_KOKKOS_DEEP_COPY, TIME_KOKKOS_DEEP_COPY_VERBOSE1,
    TIME_KOKKOS_DEEP_COPY_VERBOSE2, TIME_KOKKOS_FENCE, TIME_KOKKOS_FUNCTIONS);
 
// clang-format off
std::map<std::string, std::map<std::string, bool> > namedVariableMap_;
bool verboseDisabled_ = false;
bool timingDisabled_ = false;
}
 
namespace { // (anonymous)
 
  enum EnvironmentVariableState
  {
    EnvironmentVariableIsSet_ON,
    EnvironmentVariableIsSet_OFF,
    EnvironmentVariableIsSet,
    EnvironmentVariableIsNotSet
  };
 
  // See example here:
  //
  // http://en.cppreference.com/w/cpp/string/byte/toupper
  std::string stringToUpper (std::string s)
  {
    std::transform (s.begin (), s.end (), s.begin (),
                    [] (unsigned char c) { return std::toupper (c); });
    return s;
  }
 
  void
  split(const std::string_view s,
        std::function<void(const std::string&)> f,
        const char sep=',')
  {
    typedef std::string::size_type size_type;
    size_type cur_pos, last_pos=0, length=s.length();
    while(last_pos < length + 1)
    {
      cur_pos = s.find_first_of(sep, last_pos);
      if(cur_pos == std::string::npos)
      {
        cur_pos = length;
      }
      if(cur_pos!=last_pos) {
        auto token = std::string(s.data()+last_pos, (size_type)cur_pos-last_pos);
        f(token);
      }
      last_pos = cur_pos + 1;
     }
    return;
  }
 
  EnvironmentVariableState
  environmentVariableState(const std::string& environmentVariableValue)
  {
    std::string v = stringToUpper(environmentVariableValue);
    if      (v == "1" || v == "YES" || v == "TRUE"  || v == "ON")
      // Environment variable is "ON"
      return EnvironmentVariableIsSet_ON;
    else if (v == "0" || v == "NO"  || v == "FALSE" || v == "OFF")
      // Environment variable is "OFF"
      return EnvironmentVariableIsSet_OFF;
    // Environment has some other non-boolean value
    return EnvironmentVariableIsSet;
  }
 
  void
  setEnvironmentVariableMap (const char environmentVariableName[],
                             std::map<std::string,std::map<std::string, bool> >& valsMap,
                             const bool defaultValue)
  {
    using std::map;
    using std::getenv;
    using std::string;
    using std::vector;
 
    // Set the default value for this variable
    valsMap[environmentVariableName] = map<string,bool>{{"DEFAULT", defaultValue}};
 
    const char* varVal = getenv (environmentVariableName);
    if (varVal == nullptr) {
      // Environment variable is not set, use the default value for any named
      // variants
      return;
    }
 
    // Variable is not empty.
    const string varStr(varVal);
    vector<string> names;
    split(varStr, [&](const string& x){names.push_back(x);});
    for (auto const& name: names) {
      auto state = environmentVariableState(name);
      if (state == EnvironmentVariableIsSet_ON) {
        // Environment variable was set as ENVAR_NAME=[1,YES,TRUE,ON]
        // Global value takes precedence
        valsMap[environmentVariableName]["DEFAULT"] = true;
      }
      else if (state == EnvironmentVariableIsSet_OFF) {
        // Environment variable was set as ENVAR_NAME=[0,NO,FALSE,OFF]
        // Global value takes precedence
        valsMap[environmentVariableName]["DEFAULT"] = false;
      }
      else {
        // Environment variable was set as ENVAR_NAME=...:name:...
        // So we set the mapping true for this named variant
        valsMap[environmentVariableName][name] = true;
      }
    }
    return;
  }
 
  bool
  idempotentlyGetNamedEnvironmentVariableAsBool (const char name[],
                                                 bool& initialized,
                                                 const char environmentVariableName[],
                                                 const bool defaultValue)
  {
    using BehaviorDetails::namedVariableMap_;
    if (! initialized) {
      setEnvironmentVariableMap (environmentVariableName,
                                 namedVariableMap_,
                                 defaultValue);
      initialized = true;
    }
    auto thisEnvironmentVariableMap = namedVariableMap_[environmentVariableName];
    auto thisEnvironmentVariable = thisEnvironmentVariableMap.find(name);
    if (thisEnvironmentVariable != thisEnvironmentVariableMap.end())
      return thisEnvironmentVariable->second;
    return thisEnvironmentVariableMap["DEFAULT"];
  }
// clang-format on
 
template <typename T>
T getEnvironmentVariable(const std::string_view environmentVariableName,
                         const T defaultValue) {
  const char prefix[] = "Tpetra::Details::Behavior: ";
 
  const char *varVal = std::getenv(environmentVariableName.data());
  if (varVal == nullptr) {
    return defaultValue;
  } else {
    std::stringstream ss(varVal);
    T parsed;
    ss >> parsed;
 
    TEUCHOS_TEST_FOR_EXCEPTION(!ss, std::out_of_range,
                               prefix << "Environment "
                                         "variable \""
                                      << environmentVariableName
                                      << "\" has a "
                                         "value "
                                      << varVal
                                      << " that cannot be parsed as a "
                                      << typeid(T).name() << ".");
 
    return parsed;
  }
}
 
// full specialization of bool to preserve historical Tpetra parsing behavior
template <>
bool getEnvironmentVariable<bool>(
    const std::string_view environmentVariableName, const bool defaultValue) {
  const char *varVal = std::getenv(environmentVariableName.data());
  bool retVal = defaultValue;
  if (varVal != nullptr) {
    auto state = environmentVariableState(std::string(varVal));
    if (state == EnvironmentVariableIsSet_ON)
      retVal = true;
    else if (state == EnvironmentVariableIsSet_OFF)
      retVal = false;
  }
  return retVal;
}
 
template <>
size_t
getEnvironmentVariable<size_t>(const std::string_view environmentVariableName,
                               const size_t defaultValue) {
  const char prefix[] = "Tpetra::Details::Behavior: ";
 
  const char *varVal = std::getenv(environmentVariableName.data());
  if (varVal == nullptr) {
    return defaultValue;
  } else {
    long long val = std::stoll(stringToUpper(varVal));
    if (val < static_cast<long long>(0)) {
      // If negative - user has requested threshold be lifted
      return std::numeric_limits<size_t>::max();
    }
    if (sizeof(long long) > sizeof(size_t)) {
      // It's hard to test this code, but I want to try writing it
      // at least, in case we ever have to run on 32-bit machines or
      // machines with sizeof(long long)=16 and sizeof(size_t)=8.
      constexpr long long maxSizeT =
          static_cast<long long>(std::numeric_limits<size_t>::max());
      TEUCHOS_TEST_FOR_EXCEPTION(
          val > maxSizeT, std::out_of_range,
          prefix << "Environment "
                    "variable \""
                 << environmentVariableName
                 << "\" has a "
                    "value "
                 << val << " larger than the largest size_t value " << maxSizeT
                 << ".");
    }
    return static_cast<size_t>(val);
  }
}
 
template <typename T>
T idempotentlyGetEnvironmentVariable(
    T &value, bool &initialized, const std::string_view environmentVariableName,
    const T defaultValue) {
  if (!initialized) {
    value = getEnvironmentVariable<T>(environmentVariableName, defaultValue);
    initialized = true;
  }
  return value;
}
 
// clang-format off
  constexpr bool debugDefault () {
#ifdef HAVE_TPETRA_DEBUG
    return true;
#else
    return false;
#endif // HAVE_TPETRA_DEBUG
  }
 
  constexpr bool verboseDefault () {
    return false;
  }
 
  constexpr bool timingDefault () {
    return false;
  }
 
  constexpr bool assumeMpiIsGPUAwareDefault () {
#ifdef TPETRA_ASSUME_GPU_AWARE_MPI
    return true;
#else
    return false;
#endif // TPETRA_ASSUME_GPU_AWARE_MPI
  }
 
  constexpr bool cudaLaunchBlockingDefault () {
    return false;
  }
 
  constexpr bool hierarchicalUnpackDefault () {
    return true;
  }
 
} // namespace (anonymous)
// clang-format on
 
void Behavior::reject_unrecognized_env_vars() {
 
  static bool once = false;
 
  if (!once) {
    const char prefix[] = "Tpetra::Details::Behavior: ";
    char **env;
#if defined(WIN) && (_MSC_VER >= 1900)
    env = *__p__environ();
#else
    env = environ; // defined at the top of this file as extern char **environ;
#endif
    for (; *env; ++env) {
 
      std::string name;
      std::string value;
      const std::string_view ev(*env);
 
      // split name=value on the first =, everything before = is name
      split(
          ev,
          [&](const std::string &s) {
            if (name.empty()) {
              name = s;
            } else {
              value = s;
            }
          },
          '=');
 
      if (name.size() >= BehaviorDetails::RESERVED_PREFIX.size() &&
          name.substr(0, BehaviorDetails::RESERVED_PREFIX.size()) ==
              BehaviorDetails::RESERVED_PREFIX) {
        const auto it = std::find(BehaviorDetails::RECOGNIZED_VARS.begin(),
                                  BehaviorDetails::RECOGNIZED_VARS.end(), name);
        TEUCHOS_TEST_FOR_EXCEPTION(
            it == BehaviorDetails::RECOGNIZED_VARS.end(), std::out_of_range,
            prefix << "Environment "
                      "variable \""
                   << name << "\" (prefixed with \""
                   << BehaviorDetails::RESERVED_PREFIX
                   << "\") is not a recognized Tpetra variable.");
      }
    }
 
    once = true;
  }
}
 
bool Behavior::debug() {
  constexpr bool defaultValue = debugDefault();
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::DEBUG, defaultValue);
}
 
bool Behavior::verbose() {
  if (BehaviorDetails::verboseDisabled_)
    return false;
 
  constexpr bool defaultValue = verboseDefault();
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::VERBOSE, defaultValue);
}
 
bool Behavior::timing() {
  if (BehaviorDetails::timingDisabled_)
    return false;
 
  constexpr bool defaultValue = timingDefault();
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::TIMING, defaultValue);
}
 
bool Behavior::assumeMpiIsGPUAware() {
  constexpr bool defaultValue = assumeMpiIsGPUAwareDefault();
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::ASSUME_GPU_AWARE_MPI,
      defaultValue);
}
 
bool Behavior::cudaLaunchBlocking() {
  constexpr bool defaultValue = cudaLaunchBlockingDefault();
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::CUDA_LAUNCH_BLOCKING,
      defaultValue);
}
 
int Behavior::TAFC_OptimizationCoreCount() {
  constexpr int _default = 3000;
  static int value_ = _default;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::MM_TAFC_OptimizationCoreCount,
      _default);
}
 
size_t Behavior::verbosePrintCountThreshold() {
  constexpr size_t defaultValue(200);
 
  static size_t value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::VERBOSE_PRINT_COUNT_THRESHOLD,
      defaultValue);
}
 
size_t Behavior::rowImbalanceThreshold() {
  constexpr size_t defaultValue(256);
 
  static size_t value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::ROW_IMBALANCE_THRESHOLD,
      defaultValue);
}
 
bool Behavior::useMergePathMultiVector() {
  constexpr bool defaultValue = false;
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::MULTIVECTOR_USE_MERGE_PATH,
      defaultValue);
}
 
size_t Behavior::multivectorKernelLocationThreshold() {
  constexpr size_t defaultValue(22000);
 
  static size_t value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::VECTOR_DEVICE_THRESHOLD,
      defaultValue);
}
 
size_t Behavior::hierarchicalUnpackBatchSize() {
 
#ifdef HAVE_TPETRA_INST_CUDA
  constexpr size_t defaultValue(16);
#else
  constexpr size_t defaultValue(256);
#endif
 
  static size_t value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::HIERARCHICAL_UNPACK_BATCH_SIZE,
      defaultValue);
}
 
size_t Behavior::hierarchicalUnpackTeamSize() {
#ifdef HAVE_TPETRA_INST_CUDA
  const size_t defaultValue(16);
#else
  const size_t defaultValue(Teuchos::OrdinalTraits<size_t>::invalid());
#endif
 
  static size_t value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::HIERARCHICAL_UNPACK_TEAM_SIZE,
      defaultValue);
}
 
bool Behavior::profilingRegionUseTeuchosTimers() {
  constexpr bool defaultValue(false);
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::USE_TEUCHOS_TIMERS, defaultValue);
}
 
bool Behavior::profilingRegionUseKokkosProfiling() {
  constexpr bool defaultValue(false);
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::USE_KOKKOS_PROFILING,
      defaultValue);
}
 
bool Behavior::debug(const char name[]) {
  constexpr bool defaultValue = false;
 
  static bool initialized_ = false;
  return idempotentlyGetNamedEnvironmentVariableAsBool(
      name, initialized_, BehaviorDetails::DEBUG.data(), defaultValue);
}
 
bool Behavior::verbose(const char name[]) {
  if (BehaviorDetails::verboseDisabled_)
    return false;
 
  constexpr bool defaultValue = false;
 
  static bool initialized_ = false;
  return idempotentlyGetNamedEnvironmentVariableAsBool(
      name, initialized_, BehaviorDetails::VERBOSE.data(), defaultValue);
}
 
void Behavior::enable_verbose_behavior() {
  BehaviorDetails::verboseDisabled_ = false;
}
 
void Behavior::disable_verbose_behavior() {
  BehaviorDetails::verboseDisabled_ = true;
}
 
bool Behavior::timing(const char name[]) {
  if (BehaviorDetails::timingDisabled_)
    return false;
 
  constexpr bool defaultValue = false;
 
  static bool initialized_ = false;
  return idempotentlyGetNamedEnvironmentVariableAsBool(
      name, initialized_, BehaviorDetails::TIMING.data(), defaultValue);
}
 
void Behavior::enable_timing() { BehaviorDetails::timingDisabled_ = false; }
 
void Behavior::disable_timing() { BehaviorDetails::timingDisabled_ = true; }
 
bool Behavior::hierarchicalUnpack() {
  constexpr bool defaultValue = hierarchicalUnpackDefault();
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::HIERARCHICAL_UNPACK, defaultValue);
}
 
bool Behavior::skipCopyAndPermuteIfPossible() {
  constexpr bool defaultValue(false);
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::SKIP_COPY_AND_PERMUTE,
      defaultValue);
}
 
bool Behavior::fusedResidual() {
#if defined(KOKKOSKERNELS_ENABLE_TPL_CUSPARSE) || \
    defined(KOKKOSKERNELS_ENABLE_TPL_ROCSPARSE) || \
    defined(KOKKOSKERNELS_ENABLE_TPL_MKL)
  constexpr bool defaultValue(false);
#else
  constexpr bool defaultValue(true);
#endif
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::FUSED_RESIDUAL, defaultValue);
}
 
bool Behavior::overlapCommunicationAndComputation() {
  constexpr bool defaultValue(false);
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::OVERLAP, defaultValue);
}
 
size_t Behavior::spacesIdWarnLimit() {
  constexpr size_t defaultValue(16);
 
  static size_t value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::SPACES_ID_WARN_LIMIT,
      defaultValue);
}
 
bool Behavior::timeKokkosDeepCopy() {
  constexpr bool defaultValue(false);
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::TIME_KOKKOS_DEEP_COPY,
      defaultValue);
}
 
bool Behavior::timeKokkosDeepCopyVerbose1() {
  constexpr bool defaultValue(false);
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::TIME_KOKKOS_DEEP_COPY_VERBOSE1,
      defaultValue);
}
 
bool Behavior::timeKokkosDeepCopyVerbose2() {
  constexpr bool defaultValue(false);
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::TIME_KOKKOS_DEEP_COPY_VERBOSE2,
      defaultValue);
}
 
bool Behavior::timeKokkosFence() {
  constexpr bool defaultValue(false);
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::TIME_KOKKOS_FENCE, defaultValue);
}
 
bool Behavior::timeKokkosFunctions() {
  constexpr bool defaultValue(false);
 
  static bool value_ = defaultValue;
  static bool initialized_ = false;
  return idempotentlyGetEnvironmentVariable(
      value_, initialized_, BehaviorDetails::TIME_KOKKOS_FUNCTIONS,
      defaultValue);
}
 
} // namespace Details
} // namespace Tpetra