[Help-glpk] GLPK just hangs

[Manish Jain]

Hello all,

I have a cut/column generation implementation using GLPK 4.44 in Java.
I am seeing some weird behavior when I increase the problem size.
Glpk just gets stuck in an infinite loop every time after 42 iterations in my 
case. The problem size is big here (details in the attachment).

The weirdness is not that it just gets stuck in an infinite loop. The weird 
part is that it works fine if instead of calling lpx_simplex/lpx_integer on the 
problem that is already in memory, I write the problem to a file and load it 
again.
i.e. 
lpx_simplex(lp); 
lpx_integer(lp) <- Glpk gets stuck. There is no discernible error message. 
Output log attached.

lpx_write_cpxlp(lp, fileName)
lpx_delete_prob(lp)
lp = lpx_create_prob()
lp = lpx_read_cpxlp(fileName)
lpx_simple(lp); 
lpx_integer(lp); <- Works and gives the solution in about 2 seconds

Additionally, if I write the problem to a file when it gets stuck, then I can 
solve it with glpsol --lp fileName in a matter of 2 secs without any troubles 
as well.

Any ideas, anyone?
Also, can anyone explain to me the meaning of various lines of GLPK output, 
e.g.:
+ 49135: mip = -5.000000000e-001 <= -2.500000000e-001  50.0% (46; 6967)
Are these: [Iteration No] [Problem Class] [... ?] ( ...; row-No)

I am using GLPK-4.44 Java bindings.
The code is all in Java. 
Output log is attached. 

Thanks.

Manish Jain
University of Southern California
Hello all,

I have a cut/column generation implementation using GLPK 4.44 in Java.
I am seeing some weird behavior when I increase the problem size.
Glpk just gets stuck in an infinite loop every time after 42 iterations in my case. The problem size is big here (details in the attachment).

The weirdness is not that it just gets stuck in an infinite loop. The weird part is that it works fine if instead of calling lpx_simplex/lpx_integer on the problem that is already in memory, I write the problem to a file and load it again.

i.e. 
lpx_simplex(lp); 
lpx_integer(lp) <- Glpk gets stuck. There is no discernible error message. Output log attached.

lpx_write_cpxlp(lp, fileName)
lpx_delete_prob(lp)
lp = lpx_create_prob()
lp = lpx_read_cpxlp(fileName)

lpx_simple(lp); 
lpx_integer(lp); <- Works and gives the solution in about 2 seconds

Additionally, if I write the problem to a file when it gets stuck, then I can solve it with glpsol --lp fileName in a matter of 2 secs without any troubles as well.

Any ideas, anyone?
Also, can anyone explain to me the meaning of various lines of GLPK output, e.g.:
+ 49135: mip = -5.000000000e-001 <= -2.500000000e-001  50.0% (46; 6967)
Are these: [Iteration No] [Problem Class] [... ?] ( ...; row-No)

I am using GLPK-4.44 Java bindings.
The code is all in Java. 
Output log is attached. 

Thanks.

Manish Jain
University of Southern California