MATLAB*P PPVisualization interface

Interfacing with MATLAB*P

One of the biggest problems encountered during this package's development was simply trying to figure out and debug the scheme used to determine which portions of a given node's local data corresponded specific locations in the whole matrix. Initially, through simple experimentation, it was thought that the data layout was quite simple (which is indeed is for the row and column-wise distributions). This is the case for small matrix that is 2D block-cyclicly distributed. It's quite difficult to hunt down data layout problems for larger data sets (on the order of 1024x1024, for instance).

Despite this initially issues, a scheme was developed (and the MatrixManager class extened) to provide any node to determine both local data layout and this local data layout's mapping on to the whole, cluster-wide matrix.

This scheme, inplemented as a member of the MatrixManager class (getDistWindows(...)) returns a distribution layout data structure (DistLayout). A DistLayout data structure provides the caller with

blocks -- the number of 'blocks' of data allocated to a node.
local columns and rows -- the number of columns and rows (total) allocated for calling node's local data buffer.
block data -- an array associated with each block. Each block's attributes are enumerated here. These include the rows and columns delimiting the data in the cluster-wide maxtrix (here, x and y values) as well as the offset into the node's local data buffer (i and j) at which actual the data is located.

Aside from obtaining this information and providing the appropriate data to the rendering kernel, the PPVisual class provides a convenient interface to MATLAB. This code as the entry point for the visualization routine, provides error checking, translates some GUI requests into renderable requests (like zoom request, for example) , as well as usable return data (in this case, usually a pixel buffer) for the MATLAB "m-files" and builtin code that makeup the GUI components of the package.