Copies a submatrix from one trapezoidal matrix to another.
routinecopies the indicated matrix or submatrix of
Ato the indicated matrix or submatrix of
B. It provides a truly general copy from any block cyclicly-distributed matrix or submatrix to any other block cyclicly-distributed matrix or submatrix. With
routinesare the only ones in the ScaLAPACK library which provide inter-context operations: they can take a matrix or submatrix
A(distributed over process grid
A) and copy it to a matrix or submatrix
B(distributed over process grid
routineassumes the matrix or submatrix to be trapezoidal. Only the upper or lower part is copied, and the other part is unchanged.
There does not need to be a relationship between the two operand matrices or submatrices other than their global size and the fact that they are both legal block cyclicly-distributed matrices or submatrices. This means that they can, for example, be distributed across different process grids, have varying block sizes and differing matrix starting points, or be contained in different sized distributed matrices.
Take care when context
Ais disjoint from context
B. The general rules for which parameters need to be set are:
- All calling processes must have the correctmandn.
- Processes in contextAmust correctly define all parameters describingA.
- Processes in contextBmust correctly define all parameters describingB.
- Processes which are not members of contextAmust passctxt_a= -1 and need not set other parameters describingA.
- Processes which are not members of contextBmust passctxt_b= -1 and need not set other parameters describingB.
Because of its generality,
p?trmr2dcan be used for many operations not usually associated with copy
routines. For instance, it can be used to a take a matrix on one process and distribute it across a process grid, or the reverse. If a supercomputer is grouped into a virtual parallel machine with a workstation, for instance, this
routinecan be used to move the matrix from the workstation to the supercomputer and back. In ScaLAPACK, it is called to copy matrices from a two-dimensional process grid to a one-dimensional process grid. It can be used to redistribute matrices so that distributions p