## MB03WX

### Eigenvalues of a product of matrices in periodic Schur form

[Specification] [Arguments] [Method] [References] [Comments] [Example]

Purpose

```  To compute the eigenvalues of a product of matrices,
T = T_1*T_2*...*T_p, where T_1 is an upper quasi-triangular
matrix and T_2, ..., T_p are upper triangular matrices.

```
Specification
```      SUBROUTINE MB03WX( N, P, T, LDT1, LDT2, WR, WI, INFO )
C     .. Scalar Arguments ..
INTEGER          INFO, LDT1, LDT2, N, P
C     .. Array Arguments ..
DOUBLE PRECISION T( LDT1, LDT2, * ), WI( * ), WR( * )

```
Arguments

Input/Output Parameters

```  N       (input) INTEGER
The order of the matrix T.  N >= 0.

P       (input) INTEGER
The number of matrices in the product T_1*T_2*...*T_p.
P >= 1.

T       (input) DOUBLE PRECISION array, dimension (LDT1,LDT2,P)
The leading N-by-N part of T(*,*,1) must contain the upper
quasi-triangular matrix T_1 and the leading N-by-N part of
T(*,*,j) for j > 1 must contain the upper-triangular
matrix T_j, j = 2, ..., p.
The elements below the subdiagonal of T(*,*,1) and below
the diagonal of T(*,*,j), j = 2, ..., p, are not
referenced.

LDT1    INTEGER
The first leading dimension of the array T.
LDT1 >= max(1,N).

LDT2    INTEGER
The second leading dimension of the array T.
LDT2 >= max(1,N).

WR, WI  (output) DOUBLE PRECISION arrays, dimension (N)
The real and imaginary parts, respectively, of the
eigenvalues of T. The eigenvalues are stored in the same
order as on the diagonal of T_1. If T(i:i+1,i:i+1,1) is a
2-by-2 diagonal block with complex conjugated eigenvalues
then WI(i) > 0 and WI(i+1) = -WI(i).

```
Error Indicator
```  INFO    INTEGER
= 0:  successful exit;
< 0:  if INFO = -i, the i-th argument had an illegal
value.

```
```  None
```
Example

Program Text

```  None
```
Program Data
```  None
```
Program Results
```  None
```