Developer Reference for Intel® oneAPI Math Kernel Library for Fortran
?dttrf
Computes an LU factorization of a general tridiagonal matrix with no pivoting (local blocked algorithm).
Syntax
call sdttrf ( n , dl , d , du , info )
call ddttrf ( n , dl , d , du , info )
call cdttrf ( n , dl , d , du , info )
call zdttrf ( n , dl , d , du , info )
Include Files
mkl_scalapack.h
Description
sdttrf ddttrf cdttrf zdttrf The ?dttrf routine function computes an LU factorization of a real or complex tridiagonal matrix A using elimination without partial pivoting.
The factorization has the form A = L*U , where L is a product of unit lower bidiagonal matrices and U is upper triangular with nonzeros only in the main diagonal and first superdiagonal.
Input Parameters
n
INTEGER . The order of the matrix A(n ≥ 0) .
- dl , d , du
-
REAL for sdttrf DOUBLE PRECISION for ddttrf COMPLEX for cdttrf COMPLEX*16 for zdttrf . Arrays containing elements of A . The array dl of size (n-1) contains the sub-diagonal elements of A . The array d of size n contains the diagonal elements of A . The array du of size (n-1) contains the super-diagonal elements of A .
Output Parameters
- dl
-
Overwritten by the (n-1) multipliers that define the matrix L from the LU factorization of A .
- d
-
Overwritten by the n diagonal elements of the upper triangular matrix U from the LU factorization of A .
- du
-
Overwritten by the (n-1) elements of the first super-diagonal of U .
info
INTEGER .
= 0: successful exit < 0: if info = - i , the i -th argument had an illegal value,
> 0: if info = i , U ( i , i ) is exactly 0. The factorization has been completed, but the factor U is exactly singular. Division by 0 will occur if you use the factor U for solving a system of linear equations.