?dttrsv

Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

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ID 766686

Date 4/28/2026

Version

Public

?dttrsv

Solves a general tridiagonal system of linear equations using the LU factorization computed by ?dttrf .

Syntax

call sdttrsv ( uplo , trans , n , nrhs , dl , d , du , b , ldb , info )

call ddttrsv ( uplo , trans , n , nrhs , dl , d , du , b , ldb , info )

call cdttrsv ( uplo , trans , n , nrhs , dl , d , du , b , ldb , info )

call zdttrsv ( uplo , trans , n , nrhs , dl , d , du , b , ldb , info )

Include Files

mkl_scalapack.h

Description

sdttrsv ddttrsv cdttrsv zdttrsv The ?dttrsv routine function solves one of the following systems of linear equations:

L*X = B , L^{T}*X = B , or L^{H}*X = B ,

U*X = B , U^{T}*X = B , or U^{H}*X = B

with factors of the tridiagonal matrix A from the LU factorization computed by ?dttrf (Computes an LU factorization of a general tridiagonal matrix with no pivoting (local blocked algorithm).) .

Input Parameters

uplo: CHARACTER*1 . Specifies whether to solve with L or U .

trans

CHARACTER . Must be ‘N’ or ‘T’ or ‘C’ .

Indicates the form of the equations: If trans = 'N' , then A*X=B is solved for X (no transpose). If trans = 'T' , then A^{T}*X = B is solved for X (transpose). If trans = 'C' , then A^{H}*X = B is solved for X (conjugate transpose).

n

INTEGER . The order of the matrix A(n ≥ 0) .

nrhs

INTEGER . The number of right-hand sides, that is, the number of columns in the matrix B(nrhs ≥ 0) .

dl , d , du , b

REAL for sdttrsv DOUBLE PRECISION for ddttrsv COMPLEX for cdttrsv COMPLEX*16 for zdttrsv . The array dl of size ( n - 1) contains the ( n - 1) multipliers that define the matrix L from the LU factorization of A . The array d of size n contains n diagonal elements of the upper triangular matrix U from the LU factorization of A . The array du of size ( n - 1) contains the ( n - 1) elements of the first super-diagonal of U .

On entry, the array b of size ( ldb , nrhs ) contains the right-hand side of matrix B .

ldb

INTEGER . The leading dimension of the array b ; ldb ≥ max(1, n) .

Output Parameters

b: Overwritten by the solution matrix X .

info

INTEGER . If info=0 , the execution is successful.

If info = -i , the i -th parameter had an illegal value.

NOTE:

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Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

?dttrsv

Syntax

Include Files

Description

Input Parameters

Output Parameters