[Cbc] reading SOS item from CPLEX LP files
Kish Shen
kish.shen at gmail.com
Mon Feb 19 12:54:52 EST 2018
John,
Thanks for your reply.
There is some complications. Firstly, I have actually been using version
2.8 of Cbc that I built nearly 2 years ago. Although I did download and
build Cbc 2.9, I forgot to change a symbolic link that still pointed to
2.8, and was linking agaist that rather than 2.9.
The bigger problem is that once I correctly linked against Cbc 2.9, I get
seg faults when adding even the simplest SOS to the CbcModel.
As you may remember, we don't directly write our programs in C++ to call
Cbc, but rather the program is written in ECLiPSe, and we provide an
interface which makes the call to Cbc's API. The call that is seg faulting
is:
CbcModel* model = new CbcModel(static_cast<OsiSolverInterface
&>(*lpd->lp->S
....
model->addObjects(lpd->lp->nsos, &(lpd->lp->mipobjects[0]));
mipobjects is defined as vector<CbcObjects*>, and has been filled with the
SOS information before the addObjects call.
I am trying to generate the standalone C/C++ code from the calls that our
interface makes, but I am having some trouble getting it compiled - I have
not done this for Cbc in serveral years, and our code has undergone major
revisions since.
>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.
The program that does this is a commercial program, and I need to check if
I can send you the LP/MPS problem.
Cheers,
Kish
On Mon, Feb 19, 2018 at 4:36 PM, John Forrest <john.forrest at fastercoin.com>
wrote:
> 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
> > 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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