10.2.9 Global Reduction Functions

The global reduction functions execute various global reductions on their input. Each global reduction function corresponds to a Fortran 90 intrinsic function with the same name, minus the ``Global_'' prefix. These functions require global all-to-all communication and are relatively computationally expensive. If the code is run in serial mode, then the global reduction functions are equivalent to the serial intrinsic functions.

Calling syntax:

Output = Global_ALL (Input) ,
Output = Global_ANY (Input) ,
Output = Global_MaxVal (Input) ,
Output = Global_MinVal (Input) ,
Output = Global_Sum (Input) or
Output = Global_Dot_Product (Input1, Input2)  

Input variables:

 Input  A real or integer (in the case of Sum, MinVal and MaxVal) or a logical (in the case of ALL and ANY) scalar, vector or 2-D array that is defined on each processor and which is to be reduced over all of the processors.
 Input1, Input2  The two real, integer or logical vectors that are defined on each processor and that are to be reduced via a dot product over all of the processors.

Output variable:

 Output  The result of the global reduction.

The Global Reduction code listing contains additional documentation.

Michael L. Hall