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Hello! My name is Jackson Gorham, and I've been using the Clp solver to solve many linear programs which are relevant to my research. Recently, I been trying to solve some LPs and unfortunately Clp has been segfault'ing on me. When I run the program with its
most verbose logging option, I see the following on stdout:</div>
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<div style="font-size: 12.8px;"><font face="monospace, monospace">[Solving optimization program]</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Clp0051I Range of diagonal values is 1e+12 to 0.00074793108</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Clp0054I 241 variables killed this iteration</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Clp0058I Steps - primal 0.99429773 ,dual 0.99516802 , mu 1.4472757e-15</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Clp0035I 13 Primal 153.81162 Dual 153.81162 Complementarity 6.736505e-10 - 17621 fixed, rank 127312</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Clp0036I Feasible - objective gap 1.6454072e-09</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Clp0042I Optimal</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Clp0046I At end primal/dual infeasibilities 0/0, complementarity gap 0, objective 153.81162</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Clp0033I Barrier took 92.20 seconds (total 92.32)</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Clp0033I Crossover took 0.00 seconds (total 92.32)</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Coin0511I After Postsolve, objective 153.81162, infeasibilities - dual 0 (0), primal 0 (0)</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Clp0032I Optimal objective 153.8116218 - 26 iterations time 92.332, Presolve 0.14</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Coin0513I 1924 rows dropped after presolve pass 1</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Coin0506I Presolve 409606 (-1924) rows, 49995 (-15) columns and 1356796 (-11544) elements</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Clp0033I Presolve took 0.32 seconds (total 0.32)</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Clp0022I Absolute values of scaled rhs range from 0.005501532 to 7.9713658, minimum gap 1e+100</font></div>
<div style="font-size: 12.8px;"><font face="monospace, monospace">Clp0020I Absolute values of scaled objective range from 1.6232495e-09 to 0.002555952</font></div>
<span style="font-size: 12.8px;"><font face="monospace, monospace">Clp0021I Absolute values of scaled bounds range from 1 to 1, minimum gap 2</font></span>
<div style="font-size: 12.8px;"><font face="monospace, monospace">6.83568e+08 elements in sparse Cholesky, flop count 3.77274e+14</font></div>
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which after hanging for a while is followed by this getting printed to stderr:</div>
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<div><font face="monospace, monospace">signal (11): Segmentation fault</font></div>
<div><font face="monospace, monospace">_<wbr>ZN15ClpCholeskyBase9factorizeE<wbr>PKdPi at /home/jgorham/.julia/v0.4/Cbc/<wbr>deps/usr/lib/libClp.so (unknown line)</font></div>
<div><font face="monospace, monospace">_<wbr>ZN21ClpPredictorCorrector14cre<wbr>ateSolutionEv at /home/jgorham/.julia/v0.4/Cbc/<wbr>deps/usr/lib/libClp.so (unknown line)</font></div>
<div><font face="monospace, monospace">_<wbr>ZN21ClpPredictorCorrector5solv<wbr>eEv at /home/jgorham/.julia/v0.4/Cbc/<wbr>deps/usr/lib/libClp.so (unknown line)</font></div>
<div><font face="monospace, monospace">_<wbr>ZN10ClpSimplex12initialSolveER<wbr>8ClpSolve at /home/jgorham/.julia/v0.4/Cbc/<wbr>deps/usr/lib/libClp.so (unknown line)</font></div>
<div><font face="monospace, monospace">initial_solve_with_options at /home/jgorham/.julia/v0.4/Clp/<wbr>src/ClpCInterface.jl:190</font></div>
<div><font face="monospace, monospace">optimize! at /home/jgorham/.julia/v0.4/Clp/<wbr>src/ClpSolverInterface.jl:183</font></div>
<div><font face="monospace, monospace">jlcall_optimize!_22590 at (unknown line)</font></div>
<div><font face="monospace, monospace">jl_apply at /dev/shm/julia-0.4.0/src/gf.c:<wbr>1711</font></div>
<div><font face="monospace, monospace">solve at /home/jgorham/.julia/v0.4/<wbr>JuMP/src/solvers.jl:138</font></div>
<div><font face="monospace, monospace">julia_solve_22484 at (unknown line)</font></div>
<div><font face="monospace, monospace">jl_apply at /dev/shm/julia-0.4.0/src/gf.c:<wbr>1711</font></div>
<div><font face="monospace, monospace">affine_graph_discrepancy at util.jl:155</font></div>
<div><font face="monospace, monospace">...</font></div>
<div><font face="monospace, monospace">...</font></div>
<div><font face="monospace, monospace">srun: error: sh-26-33: task 0: Segmentation fault</font></div>
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I suspect this is due to the fact that my constraint matrix is badly conditioned... is that correct? If so, is there anything I can do to improve the preconditioning and/or get around this? Let me know if I can provide any other information that might be useful
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Thanks!</div>
~jackson
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