test_libpluto in pluto+ branch: test case 3 hangs; test case 2 hangs with GLPK

[bondhugula]

test_libpluto hangs on the third test case.

$ ./test_libpluto

*** TEST CASE 3 ***

With debug out, it appears that the call to isl hangs.

[pluto] (Band 1) Solving for hyperplane #2
[pluto] pluto_prog_constraints_lexmin (11 variables, 29 constraints)
[pluto] pluto_constraints_lexmin_isl (11 variables, 29 constraints)

With GLPK, the second test case itself hangs.

[aravindacharya]

With pip, second test hangs as well. With ISL, the second test gives the following undesired transformation
$ ./test_libpluto

*** TEST CASE 2 ***

T(S1): (i0, -4i0+p5)
loop types (loop, loop)

T(S2): (i0, -4i0-4i1+p6)
loop types (loop, loop)

This is due to the bound lower bound of -4 on transformation coefficients. If the options->coeff_bound is set to 1204, call to isl hangs

*** TEST CASE 2 ***
with debug output
[pluto] (Band 1) Solving for hyperplane #2
[pluto] pluto_prog_constraints_lexmin (34 variables, 110 constraints)
[pluto] pluto_constraints_lexmin_isl (33 variables, 110 constraints)