************80
! SUBBAK carries out back substitution for the current block.
Modified:
14 February 2007
Author:
Carl DeBoor
Reference:
Carl DeBoor,
A Practical Guide to Splines,
Springer, 2001,
ISBN: 0387953663,
LC: QA1.A647.v27.
Parameters:
Input, real ( kind = 8 ) W(NROW,NCOL), integer IPIVOT(NROW), integer
NROW, integer NCOL, integer LAST, are as on return from FACTRB.
Input/output, real ( kind = 8 ) X(NCOL).
On input, the right hand side for the equations in this block after
back substitution has been carried out up to, but not including,
equation IPIVOT(LAST). This means that X(1:LAST) contains the right hand
sides of equation IPIVOT(1:LAST) as modified during elimination,
while X(LAST+1:NCOL) is already a component of the solution vector.
On output, the components of the solution corresponding to the present
block.
| Type | Intent | Optional | Attributes | Name | ||
|---|---|---|---|---|---|---|
| real(kind=8) | :: | w(nrow,ncol) | ||||
| integer(kind=4) | :: | ipivot(nrow) | ||||
| integer(kind=4) | :: | nrow | ||||
| integer(kind=4) | :: | ncol | ||||
| integer(kind=4) | :: | last | ||||
| real(kind=8) | :: | x(ncol) |