Guide and Reference

Appendix B. Sample Programs

This appendix contains information about sample programs provided with the Parallel ESSL product.

Sample Programs and Utilities Provided with Parallel ESSL

A variety of sample programs are shipped with the Parallel ESSL product in the following directories:

• /usr/lpp/pessl.rte.common/example/c
• /usr/lpp/pessl.rte.common/example/fortran
• /usr/lpp/pessl.rte.common/example/hpf

For file names and installation procedures, see the Parallel ESSL Installation Memo.

The sample programs include:

• A diffusion calculation example program, which is discussed at length later in this chapter. Three different versions of this sample program, in C, Fortran, and HPF, are provided.

• Three sample message passing programs, image.f, pdgexmp.f, and simple.f, plus utilities in a utility library. These are provided in the Fortran directory, along with a makefile. More information regarding these programs and utilities is provided in the file /usr/lpp/pessl.rte.common/example/fortran/examples.readme. Following is a description of their functions:

  • The image program demonstrates the use of the complex to real Fourier transform subroutines and calculates a correlation between two images.

  • The pdgexmp program is a simple performance program, allowing you to vary the processor size and shape, as well as the block size, to gauge their effect on the performance of solutions to linear equations.

  • The final program, simple.f, is an example program showing how to set up and use the sample utilities.

  • The sample utility library consists of a set of Fortran 90 routines implementing commonly-used message passing functions. This example subroutine library provides you with a simplified interface to some very commonly-used message passing routines, including:

    • Library initialization:

      initutils

      BLACS initialization and initialization of library variables. This must be the first routine called in order to use the remainder of the library.

      exitutils

      Performs a BLACS grid exit and marks the library as uninitialized.

    • Scatter operation:

      scatter

      Scatter a matrix on a single node to a distributed matrix.

    • Gather operation:

      gather

      Gather a matrix onto a single node from a distributed matrix.

    • Nearest neighbor communication:

      sendnorthborder

      Sends top row of each block to north processor.

      sendwestborder

      Sends first column of each block to west processor.

      sendsouthborder

      Sends last row of each block to south processor.

      sendeastborder

      Sends last column of each block to east processor.

      rcvnorthborder

      Receives last row of each block from north processor.

      rcvwestborder

      Receives last column of each block from west processor.

      rcvsouthborder

      Receives top row of each block from south processor.

      rcveastborder

      Receives first column of each block from east processor.

    • Array creation and descriptor vector initialization:

      create_array

      Allocates memory for array and initializes array descriptor.

    • Global-to-local mapping routines:

      g2l

      Creates global to local index arrays.

      l2g

      Creates local to global index arrays.

      number_row_blocks

      Returns number of local row blocks in an array.

      number_col_blocks

      Returns number of local column blocks in an array.

      last_row_block_size

      Returns size of last local row block in an array.

      last_col_block_size

      Returns size of last local column block an in array.

• Three sample message passing programs using the sparse linear algebraic equations subroutines plus some utility programs. These programs are discussed in "Sample Sparse Linear Algebraic Equations Programs". They are provided in the Fortran directory along with a makefile. More information regarding these programs and utilities is provided in the file /usr/lpp/pessl.rte.common/example/fortran/examples.readme.