Feel::MasterStream Class Reference

Output Stream that outputs only on master rank of a worldcomm. More...

Collaboration diagram for Feel::MasterStream:

Public Types
using	LogLevel = Logger::Level

Public Member Functions
void	attachWorldComm (std::shared_ptr< WorldComm > &_wc)
void	close ()
	provides close() from std::ofstream Only closes on master rank when MPI is active
void	flush () const
	Explicit flush method.
	MasterStream (std::ostream &_out, std::shared_ptr< WorldComm > _wc=nullptr, LogLevel _log_level=Logger::Level::info)
	Construct a MasterStream from a std::ostream and optionally a WorldComm. More...
template<typename... Args>
void	open (Args... args)
	variadic template function to provide open() from std::ofstream Only opens on master rank when MPI is active
template<typename T >
const MasterStream &	operator<< (const T &v) const
	Output operator for generic types Buffers output and sends to both stream and logging backend on flush.
MasterStream const &	operator<< (std::ostream &(*F)(std::ostream &)) const
	Output operator for stream manipulators (std::endl, std::flush, etc.) Flushes buffer to both output stream and logging backend.
void	setLogLevel (LogLevel level)
	Set the log level for this stream.
std::string	str () const
	provide an interface to str() for ostringstream More...
std::shared_ptr< WorldComm >	worldCommPtr () const

Protected Attributes
std::ostringstream	buffer
	Internal buffer for line-based output.
LogLevel	log_level
	Log severity level.
std::ostream &	out
	Underlying output stream.
std::shared_ptr< WorldComm >	wc
	WorldComm for MPI rank checking.

Detailed Description

Output Stream that outputs only on master rank of a worldcomm.

The first application is to use the instantiation of MasterStream cout, cerr or clog to default output on master rank process of a Feel++ application

Environment env(...); // initialize Feel++ environment
// cout only on master rank process
cout << "Hello World from process " << Environment::rank()  << std::endl;

Behavior based on MPI state:

• Before MPI initialization: outputs on all processes (typically just one)
• After MPI initialization: outputs only on master rank
• After MPI finalization: outputs on all processes (to avoid MPI crashes)
• No MPI available: always outputs

Logging integration:

• When logging is enabled (via spdlog or glog), output is also sent to LOG(INFO/WARNING/ERROR)
• This provides automatic logging of all Feel::cout/cerr output
• Logging happens on flush (std::endl, std::flush, or explicit flush())

This ensures MasterStream is safe to use throughout the entire program lifecycle, including during global object construction/destruction.

Constructor & Destructor Documentation

MasterStream()

Feel::MasterStream::MasterStream	(	std::ostream &	_out,
		std::shared_ptr< WorldComm >	_wc = nullptr,
		LogLevel	_log_level = Logger::Level::info
	)

Construct a MasterStream from a std::ostream and optionally a WorldComm.

If no WorldComm is provided, it will be retrieved from Environment when needed.

Parameters

_out	the underlying output stream (std::cout, std::cerr, etc.)
_wc	optional WorldComm pointer (defaults to nullptr, retrieved lazily)
_log_level	the log level for logging backend (info, warn, err)

Member Function Documentation

str()

std::string Feel::MasterStream::str

(

)

const

provide an interface to str() for ostringstream

Returns

the current buffer content

worldCommPtr()

std::shared_ptr< WorldComm > Feel::MasterStream::worldCommPtr

(

)

const

Returns

the shared_ptr WorldComm