|Subject:||[Help-glpk] ERROR = basis matrix is singular to working precision|
|Date:||Thu, 30 Aug 2018 15:18:07 +0000|
I am new to GLPK and to LP solving in general
I created a model that is supposed to optimize the travel cost of technician that visit clients to repair their security system
- I have a graph of nodes and edges representing possible paths with their costs
- I have a qualification matrix to send a technician that has the required qualifications at a client site
Out of this I create constraints using the OPTANO modeling tools = mainly I create my variables, constraints and objective using OPTANO objects and it will translate this into a GLPK problem and then runs it
I have a problem understanding GLPK behavior with my model when I get this error message :
GLPK Simplex Optimizer, v4.65
5157 rows, 5980 columns, 892762 non-zeros
0: obj = 0.000000000e+000 inf = 2.300e+001 (23)
Perturbing LP to avoid stalling ...
Warning: basis matrix is ill-conditioned (cond = 1.13e+015)
Warning: basis matrix is ill-conditioned (cond = 1.45e+015)
Warning: basis matrix is ill-conditioned (cond = 1.48e+015)
Warning: basis matrix is ill-conditioned (cond = 2.2e+014)
Error: basis matrix is singular to working precision (cond = 1.54e+017)
I thought it could be numeric overflow so I added a divider to all my values in the constraints and the objective function but it did not solve my problem
Q1 : what “matrix is ill-conditioned” means ? do I have any kind of inconsistencies in my constraints ?
Q2 : what is this “working precision” ?
Q3 : what can be the source of this problem : my constraints ? my objective ?
Thank you for your help
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