TriDiag

Create a tridiagonal matrix.

Interface

܀ Interface

 MODULE PURE FUNCTION Tridiag(d, da, db, diagNo) RESULT(Ans)
    INTEGER(INT8| Int16 | Int32 | Int64 | Real32 | Real64), INTENT(IN) :: d(:)
    !! main diagonal
    INTEGER(INT8| Int16 | Int32 | Int64 | Real32 | Real64), INTENT(IN) :: da(:)
    !! super diagonal
    INTEGER(INT8| Int16 | Int32 | Int64 | Real32 | Real64) :: db(:)
    !! subdiagonal
    INTEGER(I4B), OPTIONAL, INTENT(IN) :: diagNo
    !! sub and super diagonal number, default is 1
    !! diagNo should be positive
    REAL(DFP) :: ans(SIZE(d), SIZE(d))
  END FUNCTION Tridiag

️܀ See example

This example shows the use of TriDiag method.

program main
use easifemBase
implicit none

real(dfp), allocatable :: amat(:, :), d(:), da(:), db(:)

d = ones(5, 1.0_DFP)
da = 2.0*ones(4, 1.0_DFP) !! Above diagonal
db = -2.0*ones(4, 1.0_DFP) !! Below diagonal

amat = TriDiag(d=d, da=da, db=db, diagNo=1_I4B)
call Display(MdEncode(amat), "amat = ")
end program main 

Results

amat =

1	2	0	0	0
-2	1	2	0	0
0	-2	1	2	0
0	0	-2	1	2
0	0	0	-2	1

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