[Cbc] reading SOS item from CPLEX LP files

[Kish Shen]

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>
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,"S
> 1::",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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