MatGetColumnReductions#

Gets the reductions of each column of a sparse or dense matrix.

Synopsis#

#include "petscmat.h"  
PetscErrorCode MatGetColumnReductions(Mat A, PetscInt type, PetscReal reductions[])

Input Parameters#

A - the matrix
type - A constant defined in NormType or ReductionType: NORM_2, NORM_1, NORM_INFINITY, REDUCTION_SUM_REALPART, REDUCTION_SUM_IMAGINARYPART, REDUCTION_MEAN_REALPART, REDUCTION_MEAN_IMAGINARYPART

Output Parameter#

reductions - an array as large as the TOTAL number of columns in the matrix

Note#

Each process has ALL the column reductions after the call. Because of the way this is computed each process gets all the values, if each process wants only some of the values it should extract the ones it wants from the array.

Developer Note#

This routine is primarily intended as a back-end. MatGetColumnNorms(), MatGetColumnSums(), and MatGetColumnMeans() are implemented using this routine.