NOX & LOCA: Object-Oriented Nonlinear Solver and Continuation Packages



NOX is short for Nonlinear Object-Oriented Solutions, and its objective is to enable the efficient solution of the equation: $ F(x)=0 $, where $F:\Re^n \rightarrow \Re^n$. NOX is designed to work with any linear algebra package and to be easily customized. NOX is part of Sandia's Trilinos project.

LOCA, distributed as part of NOX, is short for Library of Continuation Algorithms, and its objective is to compute families of solutions to $ F(x,p)=0 $ and their bifurcations, where $F:\Re^n\times\Re^m\rightarrow\Re^n$. For LOCA specific information, see LOCA Overview.


7/22/2005: IMPORTANT! Over the next few months, NOX will be undergoing a major refactor. Some changes that you will see in the development branch and (possibly) in the release of Trilinos 6.0 in September 2005 include:

8/29/2005: There currently is a portability issue with LOCA to the Solaris platform using the Sun Forte 7 compilers. LOCA builds on this platform but does not run correctly. It appears the problem is compiler related as the virtual table for some LOCA objects is not setup correctly. All of the LOCA examples and any LOCA tests involving continuation runs fail with a segmentation fault. It is not known whether LOCA runs correctly when built with version 10 of the Sun compilers. See bugzilla bug 1238 for more information on this issue.

8/29/2005: Many of the internals of LOCA are being rewritten to more fully support multi-parameter continuation, constraint tracking, higher-order predictors and advanced bifurcation algorithms. This process is mostly, but not fully complete. In the future, this new framework will completely replace the old framework, but for now both are available. Because the new framework is under development, most of the documentation corresponds to the old framework and therefore it is recommended that new users write their interface to the old framework. For a brief description of the new framework, see the New LOCA Framework page.

User Information

See NOX User Information

Developer Information

See NOX Developer Information

Release Information

See NOX and LOCA Release Information


NOX is available for download under the terms of the GNU Lesser General Public License.


NOX is packaged and released as part of the Trilinos Solver Framework. You may download NOX (which includes LOCA) by downloading a copy of Trilinos. Click on the Downloads reference in the left sidebar from the Trilinos Home page:

Reporting Bugs and Making Enhancement Requests

To reports bugs or make enhancement requests, visit NOX's Bugzilla (Bug Tracking) Database, and use the following instructions.

Mailing Lists

We recommend that users and developers subscribe to the following mailing lists as appropriate.

NOX & LOCA Contributors

The following people have contributed code to NOX and/or LOCA:

For All Other Questions and Comments...

Please contact Tammy Kolda ( or Roger Pawlowski (
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