Program received signal SIGSEGV, Segmentation fault.
SPARSEPACKfndsep (root=<value optimized out>, xadj=<value optimized out>, 
    adjncy=0x210fdcc, mask=0x21e071c, nsep=0x7fffbb232bac, sep=0x21e3240, 
    xls=<value optimized out>, ls=0x21e79ac) at fndsep.c:96
96                  if (xadj[nbr] > 0) {
(gdb) backtrace
#0  SPARSEPACKfndsep (root=<value optimized out>, xadj=<value optimized out>, 
    adjncy=0x210fdcc, mask=0x21e071c, nsep=0x7fffbb232bac, sep=0x21e3240, 
    xls=<value optimized out>, ls=0x21e79ac) at fndsep.c:96
#1  0x00007f42dea165d3 in SPARSEPACKgennd (neqns=0x7fffbb232c4c, 
    xadj=0x2150d4c, adjncy=0x210fdcc, mask=0x21e071c, perm=0x21e2d4c, 
    xls=0x21e537c, ls=0x21e79ac) at gennd.c:93
#2  0x00007f42def7c004 in MatGetOrdering_ND (mat=0x1f35fd0, 
    type=<value optimized out>, row=0x1ffe498, col=0x1ffe4a0) at spnd.c:22
#3  0x00007f42def6b664 in MatGetOrdering (mat=0x1f35fd0, type=0x1fff390 "nd", 
    rperm=0x1ffe498, cperm=0x1ffe4a0) at sorder.c:235
#4  0x00007f42deaf938e in PCSetUp_LU (pc=0x1ffbc00) at lu.c:124
#5  0x00007f42dee09dcb in PCSetUp (pc=0x1ffbc00) at precon.c:832
#6  0x00007f42deac3070 in KSPSetUp (ksp=0x1fc79a0) at itfunc.c:261
#7  0x00007f42deac4fbb in KSPSolve (ksp=0x1fc79a0, b=0x1e8d550, x=0x2061080)
    at itfunc.c:385
#8  0x00007f42def3ecd5 in SNES_KSPSolve (snes=0x1f750d0, ksp=0x1fc79a0, 
    b=0x1e8d550, x=0x2061080) at snes.c:4012
#9  0x00007f42deaf20f8 in SNESSolve_LS (snes=0x1f750d0) at ls.c:641
#10 0x00007f42def47975 in SNESSolve (snes=0x1f750d0, b=0x0, x=0x1e6e670)
    at snes.c:3232
#11 0x00007f42dfd02f2e in pylith::problems::SolverNonlinear::solve (
    this=0x19f7400, solution=0x1e1dd00, jacobian=<value optimized out>, 
    residual=<value optimized out>)