Reference documentation for deal.II version Git 9908a4c 20170526 11:41:54 +0200

Classes  
struct  MinMaxAvg 
class  MPI_InitFinalize 
class  Partitioner 
Functions  
unsigned int  n_mpi_processes (const MPI_Comm &mpi_communicator) 
unsigned int  this_mpi_process (const MPI_Comm &mpi_communicator) 
std::vector< unsigned int >  compute_point_to_point_communication_pattern (const MPI_Comm &mpi_comm, const std::vector< unsigned int > &destinations) 
MPI_Comm  duplicate_communicator (const MPI_Comm &mpi_communicator) 
template<typename T >  
T  sum (const T &t, const MPI_Comm &mpi_communicator) 
template<typename T , unsigned int N>  
void  sum (const T(&values)[N], const MPI_Comm &mpi_communicator, T(&sums)[N]) 
template<typename T >  
void  sum (const std::vector< T > &values, const MPI_Comm &mpi_communicator, std::vector< T > &sums) 
template<typename T >  
void  sum (const Vector< T > &values, const MPI_Comm &mpi_communicator, Vector< T > &sums) 
template<typename T >  
T  max (const T &t, const MPI_Comm &mpi_communicator) 
template<typename T , unsigned int N>  
void  max (const T(&values)[N], const MPI_Comm &mpi_communicator, T(&maxima)[N]) 
template<typename T >  
void  max (const std::vector< T > &values, const MPI_Comm &mpi_communicator, std::vector< T > &maxima) 
template<typename T >  
T  min (const T &t, const MPI_Comm &mpi_communicator) 
template<typename T , unsigned int N>  
void  min (const T(&values)[N], const MPI_Comm &mpi_communicator, T(&minima)[N]) 
template<typename T >  
void  min (const std::vector< T > &values, const MPI_Comm &mpi_communicator, std::vector< T > &minima) 
MinMaxAvg  min_max_avg (const double my_value, const MPI_Comm &mpi_communicator) 
bool  job_supports_mpi () 
A namespace for utility functions that abstract certain operations using the Message Passing Interface (MPI) or provide fallback operations in case deal.II is configured not to use MPI at all.
unsigned int Utilities::MPI::n_mpi_processes  (  const MPI_Comm &  mpi_communicator  ) 
Return the number of MPI processes there exist in the given communicator object. If this is a sequential job, it returns 1.
unsigned int Utilities::MPI::this_mpi_process  (  const MPI_Comm &  mpi_communicator  ) 
Return the rank of the present MPI process in the space of processes described by the given communicator. This will be a unique value for each process between zero and (less than) the number of all processes (given by get_n_mpi_processes()).
std::vector< unsigned int > Utilities::MPI::compute_point_to_point_communication_pattern  (  const MPI_Comm &  mpi_comm, 
const std::vector< unsigned int > &  destinations  
) 
Consider an unstructured communication pattern where every process in an MPI universe wants to send some data to a subset of the other processors. To do that, the other processors need to know who to expect messages from. This function computes this information.
mpi_comm  A communicator that describes the processors that are going to communicate with each other. 
destinations  The list of processors the current process wants to send information to. This list need not be sorted in any way. If it contains duplicate entries that means that multiple messages are intended for a given destination. 
MPI_Comm Utilities::MPI::duplicate_communicator  (  const MPI_Comm &  mpi_communicator  ) 
Given a communicator, generate a new communicator that contains the same set of processors but that has a different, unique identifier.
This functionality can be used to ensure that different objects, such as distributed matrices, each have unique communicators over which they can interact without interfering with each other.
When no longer needed, the communicator created here needs to be destroyed using MPI_Comm_free
.
T Utilities::MPI::sum  (  const T &  t, 
const MPI_Comm &  mpi_communicator  
) 
Return the sum over all processors of the value t
. This function is collective over all processors given in the communicator. If deal.II is not configured for use of MPI, this function simply returns the value of t
. This function corresponds to the MPI_Allreduce
function, i.e. all processors receive the result of this operation.
MPI_Reduce
function instead of the MPI_Allreduce
function. The latter is at most twice as expensive, so if you are concerned about performance, it may be worthwhile investigating whether your algorithm indeed needs the result everywhere.T
, namely float, double, int, unsigned int
. void Utilities::MPI::sum  (  const T(&)  values[N], 
const MPI_Comm &  mpi_communicator,  
T(&)  sums[N]  
) 
Like the previous function, but take the sums over the elements of an array of length N. In other words, the ith element of the results array is the sum over the ith entries of the input arrays from each processor.
Input and output arrays may be the same.
void Utilities::MPI::sum  (  const std::vector< T > &  values, 
const MPI_Comm &  mpi_communicator,  
std::vector< T > &  sums  
) 
Like the previous function, but take the sums over the elements of a std::vector. In other words, the ith element of the results array is the sum over the ith entries of the input arrays from each processor.
Input and output vectors may be the same.
void Utilities::MPI::sum  (  const Vector< T > &  values, 
const MPI_Comm &  mpi_communicator,  
Vector< T > &  sums  
) 
Like the previous function, but take the sums over the elements of a Vector<T>.
Input and output vectors may be the same.
T Utilities::MPI::max  (  const T &  t, 
const MPI_Comm &  mpi_communicator  
) 
Return the maximum over all processors of the value t
. This function is collective over all processors given in the communicator. If deal.II is not configured for use of MPI, this function simply returns the value of t
. This function corresponds to the MPI_Allreduce
function, i.e. all processors receive the result of this operation.
MPI_Reduce
function instead of the MPI_Allreduce
function. The latter is at most twice as expensive, so if you are concerned about performance, it may be worthwhile investigating whether your algorithm indeed needs the result everywhere.T
, namely float, double, int, unsigned int
. void Utilities::MPI::max  (  const T(&)  values[N], 
const MPI_Comm &  mpi_communicator,  
T(&)  maxima[N]  
) 
Like the previous function, but take the maxima over the elements of an array of length N. In other words, the ith element of the results array is the maximum of the ith entries of the input arrays from each processor.
Input and output arrays may be the same.
void Utilities::MPI::max  (  const std::vector< T > &  values, 
const MPI_Comm &  mpi_communicator,  
std::vector< T > &  maxima  
) 
Like the previous function, but take the maximum over the elements of a std::vector. In other words, the ith element of the results array is the maximum over the ith entries of the input arrays from each processor.
Input and output vectors may be the same.
T Utilities::MPI::min  (  const T &  t, 
const MPI_Comm &  mpi_communicator  
) 
Return the minimum over all processors of the value t
. This function is collective over all processors given in the communicator. If deal.II is not configured for use of MPI, this function simply returns the value of t
. This function corresponds to the MPI_Allreduce
function, i.e. all processors receive the result of this operation.
MPI_Reduce
function instead of the MPI_Allreduce
function. The latter is at most twice as expensive, so if you are concerned about performance, it may be worthwhile investigating whether your algorithm indeed needs the result everywhere.T
, namely float, double, int, unsigned int
. void Utilities::MPI::min  (  const T(&)  values[N], 
const MPI_Comm &  mpi_communicator,  
T(&)  minima[N]  
) 
Like the previous function, but take the minima over the elements of an array of length N. In other words, the ith element of the results array is the minimum of the ith entries of the input arrays from each processor.
Input and output arrays may be the same.
void Utilities::MPI::min  (  const std::vector< T > &  values, 
const MPI_Comm &  mpi_communicator,  
std::vector< T > &  minima  
) 
Like the previous function, but take the minimum over the elements of a std::vector. In other words, the ith element of the results array is the minimum over the ith entries of the input arrays from each processor.
Input and output vectors may be the same.
MinMaxAvg Utilities::MPI::min_max_avg  (  const double  my_value, 
const MPI_Comm &  mpi_communicator  
) 
Return sum, average, minimum, maximum, processor id of minimum and maximum as a collective operation of on the given MPI communicator mpi_communicator
. Each processor's value is given in my_value
and the result will be returned. The result is available on all machines.
MPI_Reduce
function instead of the MPI_Allreduce
function. The latter is at most twice as expensive, so if you are concerned about performance, it may be worthwhile investigating whether your algorithm indeed needs the result everywhere. bool Utilities::MPI::job_supports_mpi  (  ) 
Return whether (i) deal.II has been compiled to support MPI (for example by compiling with CXX=mpiCC
) and if so whether (ii) MPI_Init()
has been called (for example using the Utilities::MPI::MPI_InitFinalize class). In other words, the result indicates whether the current job is running under MPI.