HP MLIB User's Guide Vol. 2 7th Ed.

712 HP MLIB LAPACK User’s Guide
ScaLAPACK arguments
Array descriptor for in-core narrow band and tridiagonal matrices
The array descriptor DESC_ is an integer array of length 7. This descriptor type
is used in the ScaLAPACK narrow band routines and tridiagonal routines to
specify a block-column distribution of a global array over a one-dimensional
process grid. In the general and symmetric positive definite banded and
tridiagonal routines, a one-dimensional block-column distribution is specified
for the coefficient matrix. The matrix of right-hand-side vectors must be
distributed over a one-dimensional process grid using a block-row data
distribution.
Table 10-9 Content of the Array Descriptor for In-Core Narrow Band and
Tridiagonal Coefficient Matrices
Array descriptor for the matrix of right-hand-side vectors
The array descriptor DESC_ is an integer array of length 7. This descriptor type
is used in the ScaLAPACK narrow band routines and tridiagonal routines to
specify the block-row distribution of a global array containing the
right-hand-side vectors over a one-dimensional process grid. In the narrow
band and tridiagonal routines, a one-dimensional block-column distribution is
specified for the coefficient matrix. The matrix of right-hand-side vectors
however must be distributed over a one-dimensional process grid according to a
block-row data distribution scheme.
DESC_( ) Symbolic
Name
Scope Definition
1 DTYPE_A (global)
The descriptor type (DTYPE_A=501) for
1 x P
c
process grid for band and
tridiagonal matrices block-column
distributed.
2 CTXT_A (global)
The BLACS context handle, indicating
the BLACS process grid over which the
global matrix A is distributed. The
context itself is global, but the handle
(the integer value) may vary.
3 N_A (global)
The number of columns in the global
matrix A.
4 NB_A (global) The column block size.
5 CSRC_A (global)
The process column over which the first
column of the global matrix A is
distributed.
6 LLD_A (local)
The leading dimension of the local
array. For the tridiagonal subroutines,
this entry is ignored.
7 Unused, reserved.