|
|
IDL Reference Guide: Procedures and Functions |
|
The LUMPROVE function uses LU decomposition to iteratively improve an approximate solution X of a set of n linear equations in n unknowns Ax = b.
LUMPROVE is based on the routine mprove described in section 2.5 of Numerical Recipes in C: The Art of Scientific Computing (Second Edition), published by Cambridge University Press, and is used by permission.
| Note If you are working with complex inputs, use the LA_LUMPROVE function instead. |
Result = LUMPROVE( A, Alud, Index, B, X [, /COLUMN] [, /DOUBLE] )
The result is a vector, whose type and length are identical to X, containing the improved solution.
The n by n coefficient array of the linear system Ax = b.
The n by n LU decomposition of A created by the LUDC procedure.
An input vector, created by the LUDC procedure, containing a record of the row permutations which occurred as a result of partial pivoting.
An n-element vector containing the right-hand side of the linear system
Ax = b.
An n-element vector containing the approximate solution of the linear system
Ax = b.
Set this keyword if the input array A is in column-major format (composed of column vectors) rather than in row-major format (composed of row vectors).
Set this keyword to force the computation to be done in double-precision arithmetic.
This example uses LUMPROVE to improve an approximate solution X to the linear system Ax = B:
; Create coefficient array A: A = [[ 2.0, 1.0, 1.0], $ [ 4.0, -6.0, 0.0], $ [-2.0, 7.0, 2.0]] ; Create a duplicate of A: alud = A ; Define the right-hand side vector B: B = [3.0, -8.0, 10.0] ; Begin with an estimated solution X: X = [.89, 1.78, -0.88] ; Decompose the duplicate of A: LUDC, alud, INDEX ; Compute an improved solution: result = LUMPROVE(A, alud, INDEX, B, X) ; Print the result: PRINT, result
IDL prints:
1.00000 2.00000 -1.00000
This is the exact solution vector.
IDL Online Help (March 06, 2007)