Changes between Version 2 and Version 3 of FAQ

Aug 26, 2005 6:39:43 PM (14 years ago)

Added New vs Old


  • FAQ

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    88[ Ipopt Homepage]
     10== What is the difference between the Fortran version and the C++ version? ==
     11The original version of Ipopt was written in Fortran 77 by Andreas Waechter at Carnegie Mellon University. This version was contributed to the COIN-OR initiative and development has continued. In an effort to make Ipopt more flexible for new algorithm development, we set out to design and implement a new version of Ipopt in C++. This version was released on Aug. 26, 2005, and will be the primary version for new developments. The previous Fortran version is still available, but will not see any new development other than bug fixes.
     13Currently, there are some features in the Fortran version that are not implemented in the C++ version.
     14 * Quasi-Newton Strategies: There is no reduced-space option in the new C++ version, but full space L-BFGS and L-SR1 options are slated for development.
     15 * Complementarities: Handling of complementarity constraints using Arvind Raghunathan's constraint relaxation is not implemented.
     17The new C++ version also contains features not available in the Fortran version.
     18 * New problem structure: The new problem structure handles general inequalities. This means that slack variables are handled by Ipopt and you no longer need to add them yourself. This also allows Ipopt to identify the slack variables and take extra steps.
     19 * Adaptive Mu Update: The new version of Ipopt includes an adaptive strategy for selecting the value of the barrier parameter. In many cases, this can reduce the number of iterations required by Ipopt.
     20[ Adaptive Barrier Strategies for Nonlinear Interior Methods]
     21 * New linear solvers: Work is underway to interface Ipopt with other linear solvers, including open-source tools. Stay posted for more news.
     23All in all we think that the new version is easier to use. Furthermore, we think it is now far easier for others to contribute to the open source project.
    1025== Who do I contact with questions about Ipopt? ==
    1126If you have any questions or comments please send a message to the [ Ipopt Mailing List] (preferred), or to andreasw at Please include detailed information about your configuration (operating system, compilers, version number of Ipopt, etc) if you are writing about a compilation or execution problem.  (Note: You need to subscribe to the mailing list before you can post a message.)