Matrix Descriptors
The matrix descriptor DESCA is associated with each global matrix that stores information about the data distribution that is required to establish the mapping between each global matrix and its corresponding process and memory location. The x_ matrix descriptor entry denotes the attribute of a global matrix. For example, M_ denotes the number of rows, and M_A the number of rows in global matrix A. The descriptor type and matrix storage mode vary according to the matrix type. The following lists the content of matrix descriptor DESCA.
Dense Matrices
A general distributed matrix A (M_ × N_) is defined by its dimensions, the size of the elementary MB_ × NB_ block used for its factorization, the coordinates of the process having in its local memory the first matrix entry (RSRC_,CSRC_), and the BLACS context (CTXT_) in which this matrix is defined. A local leading dimension LLD_ is associated with the local memory address pointing to the data structure used for the local storage of this distributed matrix.
Descriptor Name |
Scope |
Definition |
|---|---|---|
DTYPE_A |
Global |
Type of the matrix |
CTXT_A |
Global |
BLACS context handle, representing the distribution of global matrix A on the process grid |
M_A |
Global |
Number of rows in global matrix A |
N_A |
Global |
Number of columns in global matrix A |
MB_A |
Global |
Blocking factor used to distribute rows |
NB_A |
Global |
Blocking factor used to distribute columns |
RSRC_A |
Global |
Process row over which the first row of matrix A is distributed |
CSRC_A |
Global |
Process column over which the first column of matrix A is distributed |
LLD_A |
Local |
Leading dimension of the local matrix. |
