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man pages->IRIX man pages -> complib/sgttrs (3)
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### Contents

```
SGTTRS(3F)							    SGTTRS(3F)

```

### NAME[Toc][Back]

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

### SYNOPSIS[Toc][Back]

```     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( * )
```

### PURPOSE[Toc][Back]

```     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.

```

### ARGUMENTS[Toc][Back]

```     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
SGTTRS(3F)							    SGTTRS(3F)

```

### NAME[Toc][Back]

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

### SYNOPSIS[Toc][Back]

```     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( * )
```

### PURPOSE[Toc][Back]

```     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.

```

### ARGUMENTS[Toc][Back]

```     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

PPPPaaaaggggeeee 2222```
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