MPI_Reduce Builtin Reduction Operations
(Help Page for MCS572)

General MPI_Reduce Format:

• Fortran Subroutine:

  call MPI_Reduce([input_data],[output_result],[input_count],[input_datatype]
  
      ,[reduce_function],ROOT,[User_communication_set],[error_code])
  

• C Function:

  MPI_Reduce(&[input_pointer],&[output_pointer],[input_count],[input_datatype]
  
      ,[reduce_function],ROOT,[User_communication_set]);
  

• Alternate C Form with Output Error Code:

  [[error_code]=] MPI_Reduce(&[input_pointer], ...,[User_communication_set]);
  

• [reduce_function] Built-In List:

  MPI function     Math Meaning
  ------------     ------------
  MPI_MAX          maximum, max
  MPI_MIN          minimum, min
  MPI_MAXLOC       maximum and location of maximum
  MPI_MINLOC       minimum and location of minimum
  MPI_SUM          sum
  MPI_PROD         product
  
  MPI_LAND         logical and
  MPI_LOR          logical or
  MPI_LXOR         logical exclusive or
  
  MPI_BAND         bitwise and
  MPI_BOR          bitwise or
  MPI_BXOR         bitwise exclusive or
  

• MPI Datatype List in F90 and C for MPI_Reduce and other MPI Functions:

  F90 MPI DataType     F90 Meaning        C MPI DataType      C Meaning
  ----------------     ---------------    --------------      ---------------
  MPI_INTEGER          INTEGER            MPI_INT             (signed) int
  MPI_REAL             REAL               MPI_FLOAT           float
  MPI_DOUBLE_PRECISION REAL*8             MPI_DOUBLE          double
                                          MPI_LONG_DOUBLE     long double
  MPI_COMPLEX          COMPLEX
  MPI_LOGICAL          LOGICAL
  MPI_CHARACTER        CHARACTER(1)       MPI_SIGNED_CHAR     signed cahr
                                          MPI_UNSIGNED_CHAR   unsigned cahr
                                          MPI_SHORT           signed short int
                                          MPI_LONG            signed long int
                                          MPI_UNSIGNED        unsigned int
                                          MPI_UNSIGNED_SHORT  unsigned short int
                                          MPI_UNSIGNED_LONG   unsigned long int
  MPI_BYTE                                MPI_BYTE
  MPI_PACKED                              MPI_PACKED
  

• Also see information on other independent types:

  MPI_Type_vector( count, blocklen, stride, oldtype, &newtype ); 
  MPI_Type_commit( &newtype ); 
  MPI_Type_structure( count, array_of_len,  array_of_displs,  
                             array_of_types, &newtype );
  

Other Information:

1. Tutorial on MPI: The Message-Passing Interface by William Gropp, Argonne National Lab.

2. MPI_Reduce Trapezoidal Rule Integration Fortran Example by Peter Pacheco for his PPMPI Book.

3. MPI_Reduce C Trapezoidal Rule Integration Example by Peter Pacheco for his PPMPI Book.

4. MPI_Reduce Laplace F90 Example for MCS572 modified from PSC example.

5. MPI_Reduce Laplace C Example for MCS572 modified from PSC example.

6. MPI_Information Page for MCS572.