Belle2::Utils Namespace Reference

General utility functions. More...

Classes
struct	VisitOverload
	Helper struct for the C++17 std::visit overload pattern to allow simple use of variants. More...
class	Timer
	Small helper class that prints its lifetime when destroyed. More...

Functions
template<class... Ts>
	VisitOverload (Ts...) -> VisitOverload< Ts... >
	Function for the C++17 std::visit overload pattern to allow simple use of variants.
template<class T >
T	reduceTBranch (TBranch *branch, const std::function< T(T, T)> &f, T reduced=T())
	Reduce a branch of a TTree. More...
double	getClock ()
	Return current value of the real-time clock. More...
double	getCPUClock ()
	Return current value of the per-thread CPU clock. More...
unsigned long	getVirtualMemoryKB ()
	Returns currently used virtual memory in KB, includes swapped and not occupied memory pages and memory-mapped files.
unsigned long	getRssMemoryKB ()
	Returns the amount of memory the process actually occupies in the physical RAM of the machine.
std::string	getCommandOutput (const std::string &command, const std::vector< std::string > &arguments={}, bool searchPath=true)
	Execute a shell command and return its output.

Detailed Description

General utility functions.

Function Documentation

getClock()

double getClock

(

)

Return current value of the real-time clock.

The returned value is meant to measure relative times and does not show absolute time values.

Note

See getCPUClock() for a higher-resolution clock unaffected by wait times.

Returns

Clock value in default time unit (ns)

Definition at line 66 of file Utils.cc.

  {
    timespec ts;
    clock_gettime(CLOCK_REALTIME, &ts);
    return (ts.tv_sec * Unit::s) + (ts.tv_nsec * Unit::ns);
  }

getCPUClock()

double getCPUClock

(

)

Return current value of the per-thread CPU clock.

Returns

CPU clock value in default time unit (ns)

Definition at line 72 of file Utils.cc.

reduceTBranch()

T Belle2::Utils::reduceTBranch	(	TBranch *	branch,
		const std::function< T(T, T)> &	f,
		T	reduced = T()
	)

Reduce a branch of a TTree.

Returns

reduced branch

Definition at line 35 of file Utils.h.

    {
      T object;
      branch->SetAddress(&object);
      int nevents = branch->GetEntries();
      for (int i = 0; i < nevents; ++i) {
        branch->GetEvent(i);
        reduced = f(reduced, object);
      }
      return reduced;
    }