---
name: "spttrs"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/spttrs.f"
---

# spttrs(3)

Part of [spttrs.f(3)](/spttrs.f/3.md).

## NAME

SRC/spttrs.f

## SYNOPSIS

### Functions/Subroutines

subroutine **spttrs** (n, nrhs, d, e, b, ldb, info)\
 **SPTTRS**

## Function/Subroutine Documentation

### subroutine spttrs (integer n, integer nrhs, real, dimension( \* ) d, real, dimension( \* ) e, real, dimension( ldb, \* ) b, integer ldb, integer info)

**SPTTRS**

**Purpose:**

```
!>
!> SPTTRS solves a tridiagonal system of the form
!>    A * X = B
!> using the L*D*L**T factorization of A computed by SPTTRF.  D is a
!> diagonal matrix specified in the vector D, L is a unit bidiagonal
!> matrix whose subdiagonal is specified in the vector E, and X and B
!> are N by NRHS matrices.
!>
```

**Parameters**

*N*

```
!>          N is INTEGER
!>          The order of the tridiagonal matrix A.  N >= 0.
!>
```

*NRHS*

```
!>          NRHS is INTEGER
!>          The number of right hand sides, i.e., the number of columns
!>          of the matrix B.  NRHS >= 0.
!>
```

*D*

```
!>          D is REAL array, dimension (N)
!>          The n diagonal elements of the diagonal matrix D from the
!>          L*D*L**T factorization of A.
!>
```

*E*

```
!>          E is REAL array, dimension (N-1)
!>          The (n-1) subdiagonal elements of the unit bidiagonal factor
!>          L from the L*D*L**T factorization of A.  E can also be regarded
!>          as the superdiagonal of the unit bidiagonal factor U from the
!>          factorization A = U**T*D*U.
!>
```

*B*

```
!>          B is REAL array, dimension (LDB,NRHS)
!>          On entry, the right hand side vectors B for the system of
!>          linear equations.
!>          On exit, the solution vectors, X.
!>
```

*LDB*

```
!>          LDB is INTEGER
!>          The leading dimension of the array B.  LDB >= max(1,N).
!>
```

*INFO*

```
!>          INFO is INTEGER
!>          = 0: successful exit
!>          < 0: if INFO = -k, the k-th argument had an illegal value
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **108** of file **spttrs.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.