ERROR 10012: Unable to read file

[Nicolò Golinucci]

I have just had a very strange error running my input output model with Gurobi through PuLP.
I have been successfully running my model with several optimal solution. Then I have introduced more constraints without having changed one line of code. Nevertheless, I have this error:

“Gurobi 7.5.2 (win64) logging started 04/29/18 17:38:40

Academic license - for non-commercial use only

Gurobi Optimizer version 7.5.2 build v7.5.2rc1 (win64)

Copyright (c) 2017, Gurobi Optimization, Inc.

Error reading LP format file C:\Users\User\AppData\Local\Temp\925046280cf94068b6488db82ea1d3f1-pulp.lp at line 4

Malformed term in expression

Neighboring tokens: " nan Production_('AA,1',_'AA,Austria') + nan Production_('AA,1',_'AB,Belgium') "

ERROR 10012: Unable to read file“

How is it possible that just adding one constraint without changing anything in the code I have such error?

Thank you in advance,

Nicolò

[Tobias Achterberg]

This is more a PuLP question than a Gurobi question.

It looks like PuLP is generating the constraints from some data that you have (in a data
base or in some tables or the like), and while doing it it performs arithmetic operations.
These operations apparently lead to floating point errors that result in "Not-a-Number"
floating point numbers. For example, this can happen when you divide by zero or when the
result of some operation is so large that it does no longer fit into a double precision
floating point value (larger than 1.8e+308).

Best regards,

Tobias

[Nicolò Golinucci]

My bad, I was going to delete the post because I had realized that it was caused by a silly mistake. I did not update a matrix which lead to NaN multiplicated by other values.
Anyway, thank you very much for your answer.

Best regards,

Nicolò

Mail priva di virus. www.avg.com

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