SPARSE_DISPLAY
Sparsity Pattern of a Matrix

SPARSE_DISPLAY is a FORTRAN77 library which can read information defining a matrix of numbers and display the sparsity pattern or location of the nonzero elements using gnuplot. This operation is already available in the built-in MATLAB "spy" command.

The user can call "spy_ge" and pass in a matrix, in general (GE) format; the routine will then locate the nonzero entries, and write out a data file and a command file which together can be used to instruct gnuplot to create a sparsity plot.

If the user already has a file containing a list of pairs of indices (I,J) corresponding to nonzero matrix entries, then the user can call "spy_file", which will write out a command file only. Together, the user data file and the command file can be used to instruct gnuplot to create a sparsity plot.

Licensing:

The computer code and data files made available on this web page are distributed under the GNU LGPL license.

Languages:

SPARSE_DISPLAY is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version.

Related Data and Programs:

CG, a FORTRAN77 library which implements a simple version of the conjugate gradient (CG) method for solving a system of linear equations of the form A*x=b, suitable for situations in which the matrix A is positive definite (only real, positive eigenvalues) and symmetric.

GNUPLOT, FORTRAN77 programs which illustrate how a program can write data and command files so that gnuplot can create plots of the program results.

MM_IO, a FORTRAN90 library which reads and writes sparse linear systems stored in the Matrix Market (MM) format.

WATHEN, a FORTRAN77 library which compares storage schemes (full, banded, sparse triplet) and solution strategies (Linpack full, Linpack banded, conjugate gradient (CG)) for linear systems involving the Wathen matrix, which can arise when solving a problem using the finite element method (FEM).

Source Code:

• sparse_display.f, the source code.
• sparse_display.sh, BASH commands to compile the source code.

Examples and Tests:

• sparse_display_prb.f, a sample calling program.
• sparse_display_prb.sh, BASH commands to compile and run the sample program.
• sparse_display_prb_output.txt, the output file.
• wathen_ge_data.txt, data defining the location of the nonzero entries of the Wathen matrix.
• wathen_ge_commands.txt, gnuplot commands to display the data.
• wathen_ge.png, an image of the sparsity pattern for the Wathen matrix.
• before_data.txt, data defining the location of the nonzero entries of a matrix, as created by DEAL.II.
• before_commands.txt, gnuplot commands to display the data.
• before.png, an image of the sparsity pattern for the before matrix.
• after_data.txt, data defining the location of the nonzero entries of a matrix, as created by DEAL.II (after reordering of variables).
• after_commands.txt, gnuplot commands to display the data.
• after.png, an image of the sparsity pattern for the after matrix.
• 30x20_data.txt, data defining the location of the nonzero entries of the 30x20 matrix.
• 30x20_commands.txt, gnuplot commands to display the data.
• 30x20.png, an image of the sparsity pattern for the 30x20 matrix.

List of Routines:

• GET_UNIT returns a free FORTRAN unit number.
• SPY_FILE plots a sparsity pattern stored in a file.
• SPY_GE plots a sparsity pattern for a general storage (GE) matrix.
• TIMESTAMP prints the current YMDHMS date as a time stamp.

You can go up one level to the FORTRAN77 source codes.