Class "spam.chol.NgPeyton"

Result of a Cholesky decomposition with the NgPeyton method

Objects from the Class

Objects are created by calls of the form chol(x,method="NgPeyton", ...) and should not be created directly with a new("spam.chol.NgPeyton", ...) call.
At present, no proper print method is defined. However, the factor can be transformed into a spam object.

Methods

as.matrix

signature(x = "spam.chol.NgPeyton"): Transform the factor into a regular matrix.

as.spam

signature(x = "spam.chol.NgPeyton"): Transform the factor into a spam object.

backsolve

signature(r = "spam.chol.NgPeyton"): solving a triangular system, see solve.

forwardsolve

signature(l = "spam.chol.NgPeyton"): solving a triangular system, see solve.

c

signature(x = "spam.chol.NgPeyton"): Coerce the factor into a vector.

determinant

signature(x = "spam.chol.NgPeyton"): Calculates the determinant from the factor, see also det.

diag

signature(x = "spam.chol.NgPeyton"): Extracts the diagonal entries.

% \item{dim<-}{\code{signature(x = "spam.chol.NgPeyton")}: ... }

dim

signature(x = "spam.chol.NgPeyton"): Retrieve the dimension. Note that "dim<-" is not implemented.

display

signature(x = "spam.chol.NgPeyton"): Transformation to a spam object and display, see also display.

image

signature(x = "spam.chol.NgPeyton"): Transformation to a spam object and display, see also image.

% \item{length<-}{\code{signature(x = "spam.chol.NgPeyton")}: ... }

length

signature(x = "spam.chol.NgPeyton"): Retrieve the dimension. Note that "length<-" is not implemented.

ordering

signature(x = "spam.chol.NgPeyton"): Retrieves the ordering, in ordering.

print

signature(x = "spam.chol.NgPeyton"): Short description.

show

signature(object = "spam.chol.NgPeyton"): Short description.

summary

signature(object = "spam.chol.NgPeyton"): Description of the factor, returns (as a list) nnzR, nnzcolindices, the density of the factor density, and fill-in ratio fillin. For the use of the first two, see ‘Examples’ in chol.

t

signature(x = "spam.chol.NgPeyton"): Transformation to a spam object and transposition.

chol

signature(x = "spam.chol.NgPeyton"): Returns x unchanged.

Details

It is not possible to directly change the length, dimension and the diagonal entries of a "spam.chol.NgPeyton" object.

References

Ng, E. G. and B. W. Peyton (1993), "Block sparse Cholesky algorithms on advanced uniprocessor computers", SIAM J. Sci. Comput., 14, pp. 1034-1056.

Author

Reinhard Furrer

See also

print.spam ordering and chol

Examples

x <- spam( c(4,3,0,3,5,1,0,1,4),3)
cf <- chol( x)
cf
#> (Upper) Cholesky factor of dimension 3x3 with 5 (row-wise) nonzero elements (
#> 2.42 Kb).
#>     (The object is supposed to be used with: 'as.spam', 'backsolve', 'forwardsolve', etc.)
#> 
#> Class 'spam.chol.NgPeyton'
as.spam( cf)
#>      [,1] [,2]     [,3]
#> [1,]    2    0 0.500000
#> [2,]    0    2 1.500000
#> [3,]    0    0 1.581139
#> Class 'spam' (32-bit)


# Modify at own risk...
slotNames(cf)
#>  [1] "entries"     "colindices"  "colpointers" "rowpointers" "dimension"  
#>  [6] "pivot"       "invpivot"    "supernodes"  "snmember"    "memory"     
#> [11] "nnzA"