Arithmetic Reductions: Sums, Means, and Prods

Description

Arithmetic reductions for distributed matrices.

Usage

rowMin(x, ...)

rowMax(x, ...)

colMin(x, ...)

colMax(x, ...)

## S4 method for signature 'ddmatrix'
rowSums(x, na.rm = FALSE)

## S4 method for signature 'ddmatrix'
colSums(x, na.rm = FALSE)

## S4 method for signature 'ddmatrix'
rowMeans(x, na.rm = FALSE)

## S4 method for signature 'ddmatrix'
colMeans(x, na.rm = FALSE)

## S4 method for signature 'ddmatrix'
rowMin(x, na.rm = FALSE)

## S4 method for signature 'matrix'
rowMin(x, na.rm = FALSE)

## S4 method for signature 'ddmatrix'
colMin(x, na.rm = FALSE)

## S4 method for signature 'matrix'
colMin(x, na.rm = FALSE)

## S4 method for signature 'ddmatrix'
rowMax(x, na.rm = FALSE)

## S4 method for signature 'matrix'
rowMax(x, na.rm = FALSE)

## S4 method for signature 'ddmatrix'
colMax(x, na.rm = FALSE)

## S4 method for signature 'matrix'
colMin(x, na.rm = FALSE)

Arguments

Details

Performs the reduction operation on a distributed matrix.

There are several legitimately new operations, including rowMin(), rowMax(), colMin(), and colMax(). These implementations are not really necessary in R because one can easily (and reasonably efficiently) do something like

apply(X=x, MARGIN=1L, FUN=min, na.rm=TRUE)

But apply() on a ddmatrix is very costly, and should be used sparingly.

sd() will compute the standard deviations of the columns, equivalent to calling apply(x, MARGIN=2, FUN=sd) (which will work for distributed matrices, by the way). However, this should be much faster and use less memory than apply(). If reduce=FALSE then the return is a distributed matrix consisting of one (global) row; otherwise, an R vector is returned, with ownership of this vector determined by proc.dest.

Value

Returns a global numeric vector.

Examples

## Not run: 
# Save code in a file "demo.r" and run with 2 processors by
# > mpiexec -np 2 Rscript demo.r

library(pbdDMAT, quiet = TRUE)
init.grid()

# don't do this in production code
x <- matrix(1:9, 3)
x <- as.ddmatrix(x)

y <- sum(colMeans(x))
comm.print(y)

finalize()

## End(Not run)