[Ipopt] Question about largest Jacobian

Stefan Vigerske stefan at math.hu-berlin.de
Mon Jun 8 14:07:40 EDT 2015


On 06/08/2015 07:51 PM, Panos Lambrianides wrote:
> Hi everyone,
> I have a question about the largest size of the Jacobian for the
> constraints.
> While setting up the problem the variable nnz_jac_g is used to set up the
> number of non-zero constraint for the Jacobian.  This is of type *Index*,
> which is itself an *int* in C++.  The upper limit for int is 32767 (2^15-1).

I believe that int's are 32bit, so you get an upper limit of around 

> Is there a reason why this is an int (versus a long for example) and more
> importantly is there a way to overcome this limitation?  I would be happy
> to tweak the code if someone would point out the right places to do so.

There are some feature requests on this:

The main thing to do is to extend a number of interfaces to 3rd-party 
software (linear algebra and linear solvers) to convert Ipopt's 
Index-arrays to their int-arrays, when necessary (or convince them to 
use also a long for indices).


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