(global) Must be

'N'

or

'V'

.

Specifies if it is necessary to compute the eigenvectors:

If

jobz

=

'N'

, then only eigenvalues are computed.

If

jobz

=

'V'

, then eigenvalues and eigenvectors are computed.

(global) Must be

'U'

or

'L'

.

Specifies whether the upper or lower triangular part of the Hermitian matrix

A

is stored:

If

uplo

=

'U'

,

a

stores the upper triangular part of

A

.

If

uplo

=

'L'

,

a

stores the lower triangular part of

A

.

(global) The number of rows and columns of the matrix

A

(

n

≥

0)

.

(local).

Block cyclic array of global size

n

*

n

and local size

lld_a

*

LOC

c

(

ja

+

n

-1)

. On entry, the symmetric matrix

A

.

If

uplo

=

'U'

, only the upper triangular part of

A

is used to define the elements of the symmetric matrix.

If

uplo

=

'L'

, only the lower triangular part of

A

is used to define the elements of the symmetric matrix.

(global) The row and column indices in the global matrix

A

indicating the first row and the first column of the submatrix

A

, respectively.

(global and local) array of size

dlen_

. The array descriptor for the distributed matrix

A

. If

desca

[

ctxt_

- 1]

is incorrect,

p?syevd

cannot guarantee correct error reporting.

(global) The row and column indices in the global matrix

Z

indicating the first row and the first column of the submatrix

Z

, respectively.

(global and local) array of size

dlen_

. The array descriptor for the distributed matrix

Z

.

descz

[

ctxt_

- 1]

must equal

desca

[

ctxt_

- 1]

.

(local).

Array of size

lwork

.

(local) The size of the array

work

.

If eigenvalues are requested:

with

trilwmin

= 3*

n

+ max(

nb

*(

np

+ 1), 3*

nb

)

If

lwork

= -1

, then

lwork

is global input and a workspace query is assumed; the

function

only calculates the size required for optimal performance for all work arrays. The required workspace is returned as the first element of the corresponding work arrays, and no error message is issued by

pxerbla

.

(local) Workspace array of size

liwork

.

(local) , size of

iwork

.

liwork

= 7*

n

+ 8*

npcol

+ 2

.

On exit, the lower triangle (if

uplo

=

'L'

), or the upper triangle (if

uplo

=

'U'

) of

A

, including the diagonal, is overwritten.

(global).

Array of size

n

. If

info

= 0

,

w

contains the eigenvalues in the ascending order.

(local).

Array, global size (

n

,

n

), local size

lld_z

*

LOCc

(

jz

+

n

-1)

.

The

z

parameter contains the orthonormal eigenvectors of the matrix

A

.

On exit, returns adequate workspace to allow optimal performance.

(local).

On exit, if

liwork

> 0,

iwork

[0]

returns the optimal

liwork

.

(global)

If

info

= 0

, the execution is successful.

If

info

< 0

:

If the

i

-th argument is an array and the

j

-entry had an illegal value, then

info

= -(

i

*100+

j

)

. If the

i

-th argument is a scalar and had an illegal value, then

info

= -

i

.

If

info

>

0

:

The algorithm failed to compute the

info

/(

n

+1)

-th eigenvalue while working on the submatrix lying in global rows and columns

mod(

info

,

n

+1).