Belle2::Utils Namespace Reference

General utility functions. More...

Classes
class	Timer
	Small helper class that prints its lifetime when destroyed. More...
struct	VisitOverload
	Helper struct for the C++17 std::visit overload pattern to allow simple use of variants. 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.
double	getClock ()
	Return current value of the real-time clock.
double	getCPUClock ()
	Return current value of the per-thread CPU clock.
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 70 of file Utils.cc.

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

getCommandOutput()

std::string getCommandOutput	(	const std::string &	command,
		const std::vector< std::string > &	arguments = {},
		bool	searchPath = true )

Execute a shell command and return its output.

Definition at line 104 of file Utils.cc.

  {
    namespace bp = boost::process::v1;
    auto cmd = searchPath ? bp::search_path(command) : boost::filesystem::path(command);
    bp::ipstream cmdOut;
    bp::child child(cmd, bp::args(arguments), bp::std_in.close(), bp::std_out > cmdOut);
    char buffer[4096];
    std::string result;
    while (child.running() && cmdOut.read(buffer, sizeof(buffer))) {
      result.append(buffer, sizeof(buffer));
    }
    if (cmdOut.gcount()) result.append(buffer, cmdOut.gcount());
    return result;
  }

getCPUClock()

double getCPUClock

(

)

Return current value of the per-thread CPU clock.

Returns

CPU clock value in default time unit (ns)

Definition at line 76 of file Utils.cc.

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

getRssMemoryKB()

unsigned long getRssMemoryKB

(

)

Returns the amount of memory the process actually occupies in the physical RAM of the machine.

Definition at line 88 of file Utils.cc.

  {
    return getStatmSize().second;
  }

getVirtualMemoryKB()

unsigned long getVirtualMemoryKB

(

)

Returns currently used virtual memory in KB, includes swapped and not occupied memory pages and memory-mapped files.

Definition at line 83 of file Utils.cc.

  {
    return getStatmSize().first;
  }

reduceTBranch()

template<class T>

T 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;
    }