Dear Nigel, No libelling intended. Getting the
permission for Black Arts and especially for sacrificing cats from the
commission for ethics in science may be very time consuming. Isn't it
possible I could get some more help with the white artish "please" or
the mythical "pretty please"? I'm running
the solver on thousands of generated problems and have no way of
checking myself if the solution is good. Is there a way to get such
information from the solved, i.e., that the best guess is not more than
some reasonable delta from the optimum? What would be a reasonable time
limit if other problems get solved in seconds? In what order would you
recommend to try the algorithms in? Regards, Zephod
Dnia 13 sierpnia 2016 15:10 Nigel Galloway
<[email protected]> napisał(a):
Zephod, you may be libelling GLPK. What evidence do you have that it is in an
infinite loop. Many problems, solvable by GLPK, are known to require a time
longer than the age of the universe to complete (before quantum computers). The
below is just getting started.
GLPK uses heuristics which solve these problems in a reasonable time a lot of
the time. The worst case time is still usually longer than the age of the
universe, and usually which are worst case is unpredictable.
You may set a time limit for GLPK's execution, and obtain its best guess
so far. You may be able to prove that this guess is minimal, or close.
You can change the search algorithm GLPK is using which may find the solution
faster.
You can change the formulation of the problem. Andrew has listed some problems
which solve faster with restraints appearing to have nothing to do with the
problem. My only comment is Mmm. These are Black Arts and probably require the
sacrifice of cats or something.
--
Nigel Galloway
[email protected]
On Thu, Aug 11, 2016, at 09:04 AM, zephod wrote:
I'm using GLPK version:
#define GLP_MAJOR_VERSION 4
#define GLP_MINOR_VERSION 60
For one of the inputs (out of many thousands that I'm running) the simplex
solver goes into an infinite loop. I include part of the output below. My
question is: is there any flag I could set for GLPK to abandon this computation
after enough unsuccessful steps or something else that I could do to counteract
infinite loops.
#355894500: obj = 1.000000000e+00 inf = 0.000e+00 (134) 7
#355895000: obj = 1.000000000e+00 inf = 0.000e+00 (8) 7
#355895500: obj = 1.000000000e+00 inf = 0.000e+00 (42) 7
#355896000: obj = 1.000000000e+00 inf = 0.000e+00 (3) 7
#355896500: obj = 1.000000000e+00 inf = 0.000e+00 (59) 7
#355897000: obj = 1.000000000e+00 inf = 0.000e+00 (10) 7
#355897500: obj = 1.000000000e+00 inf = 0.000e+00 (70) 7
#355898000: obj = 1.000000000e+00 inf = 0.000e+00 (4) 7
#355898500: obj = 1.000000000e+00 inf = 0.000e+00 (19) 7
#355899000: obj = 1.000000000e+00 inf = 0.000e+00 (5) 7
#355899500: obj = 1.000000000e+00 inf = 0.000e+00 (6) 8
#355900000: obj = 1.000000000e+00 inf = 0.000e+00 (134) 7
#355900500: obj = 1.000000000e+00 inf = 0.000e+00 (8) 7
#355901000: obj = 1.000000000e+00 inf = 0.000e+00 (42) 7
#355901500: obj = 1.000000000e+00 inf = 0.000e+00 (3) 7
#355902000: obj = 1.000000000e+00 inf = 0.000e+00 (59) 7
#355902500: obj = 1.000000000e+00 inf = 0.000e+00 (10) 7
#355903000: obj = 1.000000000e+00 inf = 0.000e+00 (69) 7
#355903500: obj = 1.000000000e+00 inf = 0.000e+00 (4) 7
#355904000: obj = 1.000000000e+00 inf = 0.000e+00 (19) 7
#355904500: obj = 1.000000000e+00 inf = 0.000e+00 (5) 7
#355905000: obj = 1.000000000e+00 inf = 0.000e+00 (6) 7
#355905500: obj = 1.000000000e+00 inf = 0.000e+00 (134) 7
#355906000: obj = 1.000000000e+00 inf = 0.000e+00 (8) 7
#355906500: obj = 1.000000000e+00 inf = 0.000e+00 (42) 7
#355907000: obj = 1.000000000e+00 inf = 0.000e+00 (3) 7
#355907500: obj = 1.000000000e+00 inf = 0.000e+00 (59) 7
#355908000: obj = 1.000000000e+00 inf = 0.000e+00 (10) 7
#355908500: obj = 1.000000000e+00 inf = 0.000e+00 (70) 7
#355909000: obj = 1.000000000e+00 inf = 0.000e+00 (4) 7
#355909500: obj = 1.000000000e+00 inf = 0.000e+00 (19) 7
#355910000: obj = 1.000000000e+00 inf = 0.000e+00 (5) 7
#355910500: obj = 1.000000000e+00 inf = 0.000e+00 (6) 7
Regards,
Zephod
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