[Cbc] reading SOS item from CPLEX LP files

[John Forrest]

Kish,

In trunk stand-alone cbc does seem to write SOS information - I think I 
did something a few months ago to make it do that - but I can't remember 
what it was!

I am always interested in why Cbc is not doing well with SOS - if you 
feel you can send me the file, I can look at why it is taking so long.

John
On 19/02/18 15:36, Kish Shen wrote:
> John,
>
> Many thanks for your fix. I have downloaded abd copied the CoinLpIO 
> files as you suggested, and it does seem to work with the LP file -- I 
> had to reintroduce the spaces, as I had edited the file to remove the 
> spaces so that Cbc can read the file.
>
> On a somewhat related topic, I think the SOS information is not 
> included in a LP or MPS formatted file written by Cbc (I assume via 
> CoinUtils again). Is there anyway to include them, or is that not 
> currently supported?
>
> This was in fact the reason I was reading a LP file written by CPLEX, 
> as the file written by Cbc did not include the SOS information. I was 
> trying to compare a problem that CPLEX solved much faster than Cbc - 
> under 10 seconds compared to something like 30,000 seconds for Cbc.
>
> Thanks again!
>
> Kish
>
>
> On Sun, Feb 18, 2018 at 7:40 PM, John Forrest 
> <john.forrest at fastercoin.com <mailto:john.forrest at fastercoin.com>> wrote:
>
>     Kish,
>
>     This was more difficult to fix than I expected.  The coding for
>     readLp uses fscanf("%s") which is totally dependent on space as a
>     separator.
>
>     I think I have fixed in trunk (you can just copy over CoinLpIO.?pp
>     to stable.  I have tried it on all the .lp files I have - which is
>     not that many.  Some files had lines with more than 100K
>     characters which caused some problems.
>
>     Please can people check I have not introduced any bugs. Also if
>     you want any other cosmetic changes - now is the time to ask for them.
>
>     John Forrest
>
>     On 16/02/18 11:51, Kish Shen wrote:
>>     Hi,
>>
>>     I posted about this to coin-discuss mailing list yesterday, but
>>     it has not appear there, and there seems to be no messages for
>>     the list since Sept 2017, so I am posting this here as well, in
>>     case something is wrong with the coin-discuss mailing list.
>>
>>     I am getting errors from Cbc when reading an LP format file
>>     generated by CPLEX 12:
>>
>>     ### CoinLpIO::readLp(): bad SOS item S1
>>
>>     I assume this is from reading the SOS items in the LP file like:
>>
>>      s999:  S1 ::  x1154 : 1  x5539 : 2
>>
>>     Looking at CoinLpIO.cpp, the code expects no space between S1 and ::
>>
>>                 if
>>     (next>=buff&&(!strncmp(next,"S1::",4)||!strncmp(next,"S2::",4))) {
>>                   setType = next[1]-'0';
>>                   gotStart=true;
>>                 } else {
>>                   // error
>>                   goodLine=0;
>>                 }
>>
>>     I edited the LP file and changed all the 'S1 ::' to 'S1::', and I
>>     then got errors about x1154: repeatedly.
>>     So it looks like the error handling does not advance to the next
>>     line after finding an error.
>>
>>     I edited removed all the spaces before ':' for the SOS items, and
>>     the file was then read without errors.
>>
>>     Should ReadLp be changed to read the SOS items generated by CPLEX
>>     with the extra spaces?
>>
>>     I am running the latest stable branch of Cbc 2.9, downloaded via
>>     svn co about 2 days ago.
>>
>>     Thanks and cheers,
>>
>>     Kish
>>
>>
>>
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