* penny data file:

  See the discussion here:
  https://savannah.gnu.org/patch/?func=detailitem&item_id=8472

* west0479 data file:

  Chemical engineering plant models Eight stage column section, all
  rigorous from set CHEMWEST, from the Harwell-Boeing Collection.

  west0479.mtx: original file obtained from from
  https://math.nist.gov/MatrixMarket/data/Harwell-Boeing/chemwest/west0479.html

  west0479.mat: generated from west0479.mtx as follows:

    x = load ("west0479.mtx");
    nr = x(1,1);
    nc = x(1,2);
    i = x(2:end,1);
    j = x(2:end,2);
    sv = x(2:end,3);
    west0479 = sparse(i, j, sv, nr, nc);
    save -text west0479.mat west0479

  Note that the original file has 1910 entries but 22 of them are exact
  zeros:

    384 86  0.0000000000000e+00
    360 116  0.0000000000000e+00
    361 117  0.0000000000000e+00
    362 118  0.0000000000000e+00
    238 224  0.0000000000000e+00
    239 225  0.0000000000000e+00
    240 226  0.0000000000000e+00
    250 240  0.0000000000000e+00
    251 241  0.0000000000000e+00
    252 242  0.0000000000000e+00
    272 259  0.0000000000000e+00
    273 260  0.0000000000000e+00
    274 261  0.0000000000000e+00
    294 278  0.0000000000000e+00
    295 279  0.0000000000000e+00
    296 280  0.0000000000000e+00
    316 297  0.0000000000000e+00
    317 298  0.0000000000000e+00
    318 299  0.0000000000000e+00
    338 316  0.0000000000000e+00
    339 317  0.0000000000000e+00
    340 318  0.0000000000000e+00

  These are not explicitly included in the west0479.mat file.