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 (N-1)
The (n-1) 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 (N-1)
The (n-1) elements of the first superdiagonal of U.
DU2 (input) REAL array, dimension (N-2)
The (n-2) 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.
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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 i-th 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 (N-1)
The (n-1) 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 (N-1)
The (n-1) elements of the first superdiagonal of U.
DU2 (input) REAL array, dimension (N-2)
The (n-2) 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 i-th argument had an illegal value
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