man dgttrs (Fonctions bibliothèques) - solve one of the systems of equations AX = B or A'X = B,

NAME

DGTTRS - solve one of the systems of equations A*X = B or A'*X = B,

DGTTRS solves one of the systems of equations A*X = B or A'*X = B, with a tridiagonal matrix A using the LU factorization computed by DGTTRF.

TRANS (input) CHARACTER: Specifies the form of the system of equations. = 'N': A * X = B (No transpose)

= 'T': A'* X = B (Transpose)

= 'C': A'* X = B (Conjugate transpose = Transpose)
N (input) INTEGER: The order of the matrix A.
NRHS (input) INTEGER: The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
DL (input) DOUBLE PRECISION array, dimension (N-1): The (n-1) multipliers that define the matrix L from the LU factorization of A.
D (input) DOUBLE PRECISION array, dimension (N): The n diagonal elements of the upper triangular matrix U from the LU factorization of A.
DU (input) DOUBLE PRECISION array, dimension (N-1): The (n-1) elements of the first super-diagonal of U.
DU2 (input) DOUBLE PRECISION array, dimension (N-2): The (n-2) elements of the second super-diagonal of U.
IPIV (input) INTEGER array, dimension (N): The pivot indices; for 1 <= i <= n, row i of the matrix was interchanged with row IPIV(i). IPIV(i) will always be either i or i+1; IPIV(i) = i indicates a row interchange was not required.
B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS): On entry, the matrix of right hand side vectors B. On exit, B is overwritten by the solution vectors X.
LDB (input) INTEGER: The leading dimension of the array B. LDB >= max(1,N).
INFO (output) INTEGER: = 0: successful exit

< 0: if INFO = -i, the i-th argument had an illegal value