is_sense parsing error when < at position 1023 in a constraint line

[dlaehnemann]

I've been tripped up by a very weird bug, that led to a line parsing failure and then down the line to renamed variables, so that I could not use the eventual solution. Here's the minimal example to reproduce the problem (simply rename to the extension '.lp, GitHub doesn't allow uploads with that extension...):

buffer_size_issue.txt

When running cbc buffer_size_issue.lp solve on it, it throws:

Welcome to the CBC MILP Solver 
Version: 2.10.5 
Build Date: Dec  8 2020 

command line - cbc weird_corner_case.lp solve (default strategy 1)
### ERROR: CoinLpIO: is_sense(): string: < 
 CoinLpIO::readLp(): Maximization problem reformulated as minimization
### CoinLpIO::is_invalid_name(): Name < contains illegal character '<'
### CoinLpIO::are_invalid_names(): Invalid name: vnames[63]: <
### CoinLpIO::readLp(): Invalid column names
Now using default column names.

As deleting any single char in the c6708: line makes this error go away, and the < char (from <=) is in position 1023 of the line, and the buffer size for parsing is 1024, I am assuming it is something to do with this combination chopping up the <= and then is_sense complaining that there's only the < and no = following it in the buffer. I guess this special requires explicit handling in is_sense and maybe elsewhere, as well?

[jjhforrest]

As other solvers seem to allow any length line, I suppose we ought to fix. Will see how easy it is to fix in a reasonably elegant way. John Forrest

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On 17/02/2021 16:04, David Laehnemann wrote: I've been tripped up by a very weird bug, that led to a line parsing failure and then down the line to renamed variables, so that I could not use the eventual solution. Here's the minimal example to reproduce the problem (simply rename to the extension |'.lp|, GitHub doesn't allow uploads with that extension...): buffer_size_issue.txt <https://github.com/coin-or/CoinUtils/files/5996907/buffer_size_issue.txt> When running |cbc buffer_size_issue.lp solve| on it, it throws: |Welcome to the CBC MILP Solver Version: 2.10.5 Build Date: Dec 8 2020 command line - cbc weird_corner_case.lp solve (default strategy 1) ### ERROR: CoinLpIO: is_sense(): string: < CoinLpIO::readLp(): Maximization problem reformulated as minimization ### CoinLpIO::is_invalid_name(): Name < contains illegal character '<' ### CoinLpIO::are_invalid_names(): Invalid name: vnames[63]: < ### CoinLpIO::readLp(): Invalid column names Now using default column names. | As deleting any single char in the |c6708:| line makes this error go away, and the |<| char (from |<=|) is in position 1023 of the line, and the buffer size for parsing is 1024, I am assuming it is something to do with this combination chopping up the |<=| and then |is_sense| complaining that there's only the |<| and no |=| following it in the buffer. I guess this special requires explicit handling in is_sense and maybe elsewhere, as well? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#144>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABWJYHAXO6GSNZEDXSUSNGDS7PSKNANCNFSM4XYTUD7Q>.

[jjhforrest]

David, Hopefully fixed in master. I think the code should now cope with lines of any length and give the correct line number. I am not very familiar with code, so have not tried to redo error messages entirely. I agree that some error messags are not obviously easy to decode - this partly because the format is so flexible. So to test error handling I added a random ++. This was only picked up as error at very end when the code said + was an invalid name - because it had taken the first + as part of equation. It found the error and fixing everything may not be worthwhile. John Forrest

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On 17/02/2021 16:04, David Laehnemann wrote: I've been tripped up by a very weird bug, that led to a line parsing failure and then down the line to renamed variables, so that I could not use the eventual solution. Here's the minimal example to reproduce the problem (simply rename to the extension |'.lp|, GitHub doesn't allow uploads with that extension...): buffer_size_issue.txt <https://github.com/coin-or/CoinUtils/files/5996907/buffer_size_issue.txt> When running |cbc buffer_size_issue.lp solve| on it, it throws: |Welcome to the CBC MILP Solver Version: 2.10.5 Build Date: Dec 8 2020 command line - cbc weird_corner_case.lp solve (default strategy 1) ### ERROR: CoinLpIO: is_sense(): string: < CoinLpIO::readLp(): Maximization problem reformulated as minimization ### CoinLpIO::is_invalid_name(): Name < contains illegal character '<' ### CoinLpIO::are_invalid_names(): Invalid name: vnames[63]: < ### CoinLpIO::readLp(): Invalid column names Now using default column names. | As deleting any single char in the |c6708:| line makes this error go away, and the |<| char (from |<=|) is in position 1023 of the line, and the buffer size for parsing is 1024, I am assuming it is something to do with this combination chopping up the |<=| and then |is_sense| complaining that there's only the |<| and no |=| following it in the buffer. I guess this special requires explicit handling in is_sense and maybe elsewhere, as well? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#144>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABWJYHAXO6GSNZEDXSUSNGDS7PSKNANCNFSM4XYTUD7Q>.

[dlaehnemann]

Hi John,

the swift response is very much appreciated, and this does fix the minimal example I provided. So I'll close this issue.

However, I've found some further parsing issues and created the follow-up issues #145 and #146.

Thanks a lot and best regards,
David