LBL is a unified C interface to the multifrontal symmetric indefinite linear system solvers MA27 and MA57 from the Harwell Subroutine Library.

Here are the essential bits of a typical example (see examples/examples.c for the complete code):

#include "lbl.h"
LBL_Data *lbl;           // Main data structure.
lbl = LBL_Initialize(nnz, n, stderr, 1);
LBL_Analyze(lbl, 0);     // 0 = automatic pivot choice.
LBL_Factorize(lbl, val); // val is an array of doubles.
LBL_Solve(lbl, rhs);     // rhs is an array of doubles.
LBL_Finalize(lbl);

1. Place the source files for MA27 and MA57 in some directory. You will need fd15d.f ma27ad.f mc21d.f mc34d.f mc47d.f mc59d.f mc64d.f mc71d.f ma57d.f. See http://www.hsl.rl.ac.uk/hsl2007
2. Edit and customize make.inc
3. Type make all.

You can clean out temporary files with make clean and sanitize everything with make purge.

Type make example. Change to the example directory and type ./example.

The expected output is:

Input matrix:
1  1  2.000000
1  2  3.000000
2  3  4.000000
2  5  6.000000
3  3  1.000000
3  4  5.000000
5  5  1.000000
Input right-hand side:
8.000000 45.000000 31.000000 15.000000 17.000000
Solution:
1.000000 2.000000 3.000000 4.000000 5.000000

Please send bugs, comments, feature requests, test cases, chocolate and coffee to the Lighthouse LBL page.

Enjoy!