SGTTRS(3F) SGTTRS(3F)
SGTTRS  solve one of the systems of equations A*X = B or A'*X = B,
SUBROUTINE SGTTRS( TRANS, N, NRHS, DL, D, DU, DU2, IPIV, B, LDB, INFO )
CHARACTER TRANS
INTEGER INFO, LDB, N, NRHS
INTEGER IPIV( * )
REAL B( LDB, * ), D( * ), DL( * ), DU( * ), DU2( * )
SGTTRS 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 SGTTRF.
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. N >= 0.
NRHS (input) INTEGER
The number of right hand sides, i.e., the number of columns of
the matrix B. NRHS >= 0.
DL (input) REAL array, dimension (N1)
The (n1) multipliers that define the matrix L from the LU
factorization of A.
D (input) REAL array, dimension (N)
The n diagonal elements of the upper triangular matrix U from the
LU factorization of A.
DU (input) REAL array, dimension (N1)
The (n1) elements of the first superdiagonal of U.
DU2 (input) REAL array, dimension (N2)
The (n2) elements of the second superdiagonal 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.
Page 1
SGTTRS(3F) SGTTRS(3F)
B (input/output) REAL array, dimension (LDB,NRHS)
On entry, the right hand side matrix B. On exit, B is
overwritten by the solution matrix 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 ith argument had an illegal value
SGTTRS(3F) SGTTRS(3F)
SGTTRS  solve one of the systems of equations A*X = B or A'*X = B,
SUBROUTINE SGTTRS( TRANS, N, NRHS, DL, D, DU, DU2, IPIV, B, LDB, INFO )
CHARACTER TRANS
INTEGER INFO, LDB, N, NRHS
INTEGER IPIV( * )
REAL B( LDB, * ), D( * ), DL( * ), DU( * ), DU2( * )
SGTTRS 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 SGTTRF.
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. N >= 0.
NRHS (input) INTEGER
The number of right hand sides, i.e., the number of columns of
the matrix B. NRHS >= 0.
DL (input) REAL array, dimension (N1)
The (n1) multipliers that define the matrix L from the LU
factorization of A.
D (input) REAL array, dimension (N)
The n diagonal elements of the upper triangular matrix U from the
LU factorization of A.
DU (input) REAL array, dimension (N1)
The (n1) elements of the first superdiagonal of U.
DU2 (input) REAL array, dimension (N2)
The (n2) elements of the second superdiagonal 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.
Page 1
SGTTRS(3F) SGTTRS(3F)
B (input/output) REAL array, dimension (LDB,NRHS)
On entry, the right hand side matrix B. On exit, B is
overwritten by the solution matrix 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 ith argument had an illegal value
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