Teuchos version of MPI_MAXLOC. More...

Inheritance diagram for Teuchos::MaxLoc< Ordinal, ScalarType, IndexType >:

Public Member Functions
void	reduce (const Ordinal count, const std::pair< ScalarType, IndexType > inBuffer[], std::pair< ScalarType, IndexType > inoutBuffer[]) const

Detailed Description

template<class Ordinal, class ScalarType, class IndexType>
class Teuchos::MaxLoc< Ordinal, ScalarType, IndexType >

Teuchos version of MPI_MAXLOC.

Author:: Mark Hoemmen

Template Parameters:

Ordinal	The template parameter of `Comm`.
ScalarType	Type for which to find the maximum.
IndexType	Type indicating the index of the maximum.

MPI_MAXLOC is a standard reduction operator provided by the MPI standard. According to the standard, MPI_MAXLOC combines the (value, index) pairs (u,i) and (v,j) into (w,j), where $w = max(u,v)$ , and

$k = \begin{cases} i & \text{if $u > v$}, \\ \min(i,j) & \text{if $u = v$}, \\ j & \text{if $u < v$}. \\ \end{cases}$

This class implements the MPI_MAXLOC reduction operator for the Teuchos communication wrappers. We need to define this separately from MPI for two reasons. First, the Teuchos comm wrappers do not currently expose taking an MPI_Op. Second, we need MaxLoc to be templated on the scalar and index types, in order to match Teuchos' MPI interface.

What happens to NaN ("Not a Number")? A NaN is neither less than, greater than, or equal to any floating-point number or any NaN. We can alter the above definition slightly so that a MaxLoc reduction has a well-defined result in case the array contains a NaN:

$w = \begin{cases} u & \text{if $u > v$}, \\ v & \text{if $u < v$}. \\ u & \text{otherwise}. \\ \end{cases}$

and

$k = \begin{cases} i & \text{if $u > v$}, \\ j & \text{if $u < v$}. \\ \min(i,j) & \text{otherwise}. \\ \end{cases}$

Defining MaxLoc in this way ensures that for any array containing a NaN, the value (w) returned is the first NaN, and the index (k) returned is the index of the first NaN.

Definition at line 106 of file Teuchos_TimeMonitor.cpp.

Member Function Documentation

template<class Ordinal , class ScalarType , class IndexType >

void Teuchos::MaxLoc< Ordinal, ScalarType, IndexType >::reduce	(	const Ordinal	count,
		const std::pair< ScalarType, IndexType >	inBuffer[],
		std::pair< ScalarType, IndexType >	inoutBuffer[]
	)		const `[virtual]`

Implements Teuchos::ValueTypeReductionOp< Ordinal, std::pair< ScalarType, IndexType > >.

The documentation for this class was generated from the following file:

Teuchos_TimeMonitor.cpp

Public Member Functions

Detailed Description

template<class Ordinal, class ScalarType, class IndexType> class Teuchos::MaxLoc< Ordinal, ScalarType, IndexType >

Member Function Documentation

template<class Ordinal, class ScalarType, class IndexType>
class Teuchos::MaxLoc< Ordinal, ScalarType, IndexType >