Reduce is a collective algorithm that combines the values supplied by each process in the leaf group into a single value available at the designated root process. This particular variant of Reduce<(Of <(T>)>)(T, ReductionOperation<(Of <(T>)>), Int32) applies to each of the elements of the provided arrays. Each process must provide arrays of the same length, and the values at each array index are combined in a user-defined way, specified via a delegate. If value1, value2, ..., valueN are the ith values provided by the N processes in the communicator, the ith result will be the value value1 op value2 op ... op valueN. The resulting array is only available to the root process. If all processes need the result of the reduction, use Allreduce<(Of <(T>)>)(array<T>[]()[], ReductionOperation<(Of <(T>)>), array<T>[]()[]%).

Namespace:  MPI
Assembly:  MPI (in MPI.dll)
Version: (


public void Reduce<T>(
	T[] inValues,
	ReductionOperation<T> op,
	int root,
	ref T[] outValues
Visual Basic (Declaration)
Public Sub Reduce(Of T) ( _
	inValues As T(), _
	op As ReductionOperation(Of T), _
	root As Integer, _
	ByRef outValues As T() _
Visual C++
generic<typename T>
void Reduce(
	array<T>^ inValues, 
	ReductionOperation<T>^ op, 
	int root, 
	array<T>^% outValues


Type: array< T >[]()[]
The local values that will be combined with the values provided by other leaf group processes.
Type: MPI..::.ReductionOperation<(Of <(T>)>)
The operation used to combine two values. This operation must be associative.
Type: System..::.Int32
At leaf group processes, the rank of the process that is the root of the reduction operation, which will receive the result of the reduction operation in its outValue argument. At the root, should be Root. At non-root processes in the root group, should be Null.
Type: array< T >[]()[] %
The variable that will receive the results of the reduction operation. Only the root process will receive the actual result; all other processes will receive a default-initialized value. When this collective operation returns, outValues will be of the same length as inValues.

Type Parameters

Any serializable type.

See Also