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.
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cg is available in a C version and a C++ version and a Fortran90 version and a MATLAB version and an Octave version and a Python version.
cg_rc, a Fortran90 code which implements the conjugate gradient method for solving a positive definite sparse linear system A*x=b, using reverse communication.
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.
wathen_matrix, a Fortran90 code which compares storage schemes (full, banded, sparse triplet) and solution strategies (Linpack full, Linpack banded, conjugate gradient) for linear systems involving the Wathen matrix, which can arise when solving a problem using the finite element method (FEM).