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Add ROOT::GetAvailableThreads() helper. #754

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Add ROOT::GetAvailableThreads() helper. #754

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e850d81
Add ROOT::GetAvailableThreads() helper.
xvallspl Jul 12, 2017
082b406
Addressed suggested changes
xvallspl Jul 13, 2017
0f311b6
Add back return statement
xvallspl Jul 13, 2017
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3 changes: 2 additions & 1 deletion core/base/inc/TROOT.h
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Expand Up @@ -73,7 +73,7 @@ namespace Internal {
TParBranchProcessingRAII() { EnableParBranchProcessing(); }
~TParBranchProcessingRAII() { DisableParBranchProcessing(); }
};

// Manage parallel tree processing
void EnableParTreeProcessing();
void DisableParTreeProcessing();
Expand All @@ -95,6 +95,7 @@ namespace ROOT {
void DisableImplicitMT();
Bool_t IsImplicitMTEnabled();
UInt_t GetImplicitMTPoolSize();
UInt_t GetAvailableThreads();
}

class TROOT : public TDirectory {
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16 changes: 16 additions & 0 deletions core/base/src/TROOT.cxx
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Expand Up @@ -577,6 +577,22 @@ namespace Internal {
#endif
}

////////////////////////////////////////////////////////////////////////////////
/// Returns the maximum number of threads the user can instantiate.
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@Axel-Naumann Axel-Naumann Jul 12, 2017

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This comment is incorrect (at least for the !IMT case). Could you copy the comment from GetMaxNThreadsAvailable()?

Also this doesn't return the available threads but their number. I'd suggest to use the same name for both the TROOT member and the ROOT::Internal member.

UInt_t GetAvailableThreads()
{
#ifdef R__USE_IMT
static UInt_t (*sym)() = (UInt_t(*)())Internal::GetSymInLibImt("ROOT_TImplicitMT_GetAvailableThreads");
if (sym)
return sym();
else
return 0;
#else
SysInfo_t s;
gSystem->GetSysInfo(&s);
return s.fCpus;
#endif
}
}

TROOT *ROOT::Internal::gROOTLocal = ROOT::GetROOT();
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5 changes: 5 additions & 0 deletions core/imt/inc/ROOT/TPoolManager.hxx
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Expand Up @@ -72,6 +72,11 @@ namespace ROOT {
/// The number of threads will be able to change calling the factory function again after the last
/// remaining shared_ptr owning the object is destroyed or reasigned, which will trigger the destructor of the manager.
std::shared_ptr<TPoolManager> GetPoolManager(UInt_t nThreads = 0);


/// Get the maximum number of logical CPUs available.
/// In case of having an affinity mask (TBB), return the logical CPU available to the current process in accordance with it.
Int_t GetMaxNThreadsAvailable();
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@Axel-Naumann Axel-Naumann Jul 12, 2017

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Can you adjust the function name to the documentation? It does not return the maximum number of threads.

}
}

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4 changes: 4 additions & 0 deletions core/imt/src/TImplicitMT.cxx
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Expand Up @@ -80,6 +80,10 @@ extern "C" UInt_t ROOT_TImplicitMT_GetImplicitMTPoolSize()
return ROOT::Internal::TPoolManager::GetPoolSize();
};

extern "C" UInt_t ROOT_TImplicitMT_GetAvailableThreads()
{
return ROOT::Internal::GetMaxNThreadsAvailable();
};

extern "C" void ROOT_TImplicitMT_EnableParBranchProcessing()
{
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6 changes: 5 additions & 1 deletion core/imt/src/TPoolManager.cxx
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Expand Up @@ -51,9 +51,13 @@ namespace ROOT {
if (GetWP().expired()) {
std::shared_ptr<TPoolManager> shared(new TPoolManager(nThreads));
GetWP() = shared;
return GetWP().lock();
}
return GetWP().lock();
}

Int_t GetMaxNThreadsAvailable()
{
return tbb::task_scheduler_init::default_num_threads();
}
}
}