[Coin-ipopt] MA27 error message

Zhiwen Chong zhiwen.chong at elf.mcgill.ca
Tue Apr 11 01:47:38 EDT 2006

Thanks to everyone for their replies!

I tried linear_scaling_on_demand=no and it seems to have reduced the  
number of MA27 warnings, so I'm happy.


On 10-Apr-06, at 5:10 PM, Andreas Waechter wrote:
> There is an option to equilibriate the linear system give to MA27,  
> using MC19 (which must be included when you compile Ipopt to be  
> able to use this).  In the current C++ version of Ipopt, this  
> scaling is done only when iterative refinement fails.  However, you  
> can tell Ipopt to always use MC19 to scale the linear system, by  
> setting the option
> linear_scaling_on_demand no
> Maybe we should make this the default...  (I didn't do this,  
> because in my tests, it wasn't leading to considerable more robust  
> results, but using MC19 makes the computation quite a bit  
> slower...)  We might implement some other heuristics later, but for  
> now, please try if the above option helps. For some other users,  
> using thie option avoided the huge fill-in in MA27.
> Of course, you can also try to use some other linear solver (there  
> are new interfaces in the most recent release of Ipopt).
> Regards,
> Andreas

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