**sparse_display**,
a FORTRAN90 code which
can read information defining a matrix of numbers and display
the sparsity pattern or location of the nonzero elements using
gnuplot.

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.

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

**sparse_display** is available in
a C version and
a C++ version and
a Fortran90 version and
a MATLAB version and
an Octave version.

cg, a FORTRAN90 code 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_test, FORTRAN90 codes which write data and command files so that gnuplot() can create plots.

wathen_matrix, a FORTRAN90 code 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).

- sparse_display.f90, the source code.
- sparse_display.sh, compiles the source code.