News - Dash Optimization Announces Release of Xpress-MP 2007A

ENGLEWOOD CLIFFS, NJ and LONDON: Dash Optimization today announced the release of Xpress-MP 2007A. Xpress-MP continues to provide state-of-the-art modeling and optimization tools to customers in a wide range of vertical industries.

Xpress-MP release 2007A includes major revisions to the Optimizer LP/MIP solver, the Mosel modeling language and the Kalis constraint programming engine.

Xpress-Optimizer 18.00.01

Optimization performance has been improved across a wide range of models. The table below shows the performance comparison with release 2006A for the Dash standard QA set of models:

Algorithm 2007A improvement over 2006A

Primal 9%

Barrier 13%

MIP 41%

Presolve
- Presolve has been completely rewritten. It is now faster, especially on large models, and performs more reductions.
- Improved tightening for mixed integer models results in better solutions and reductions in solve times.
- Dualization: The LP now optimizes much faster on models with far more rows than columns.
Dual Simplex has been improved on models where it is hard to achieve dual feasibility.
Some numerical problems have been made more robust with better objective function scaling.
MIR cut generation has been improved, leading to smaller gaps and/or faster solve times for mixed integer problems.
New Network Simplex algorithm is 10 - 100 times faster than dual on network models. Advanced feasible starts are supported.
New node-to-node presolve leads to significant improvements to branch-and-bound on mixed integer models.
The local search heuristic now generates better solutions, especially at the root node.
The diving heuristic has been improved to find better solutions.
Improvements have been made to obtain faster solutions to scheduling models.
Solutions are now memory resident by default.

Xpress-Mosel 2.0.0

The new release features a multitude of improvements to the most advanced modeling environment available today:

Packages: Mosel can now be used to create external compiled libraries of functions and variables which can be imported for use in other models.
Records: Mosel now supports user-defined structure types that can encapsulate several member variables.
Complex nested types: Any structured type (array, set, list or record) can now be used as an elementary type e.g. array(range) of set of integer
A new structure 'list' replaces tuples, making it possible to declare and manipulate ordered collections of objects of a given type. Aggregate operators now accept lists as a source of values for their indices.
User types can now be declared as an alias to a complex type.
A new IO driver 'excel' provides initialization from Excel files without requiring SQL statements.
Mosel 2 includes full support for Parallel MIP multi-threading.

Constraint Programming: Xpress-Kalis

Artelys and Dash reinforce their joint efforts to provide the most advanced constraint programming functionality in the Mosel environment.

Xpress-Kalis now includes dedicated high-level functionality to ease the formulation and solving of scheduling problems.

New constraint relations representing 'disjunctive' and 'cumulative' resource constraints have been introduced.
Predefined objects such as tasks and resources provide high-level modeling support for many scheduling situations.
For solving scheduling problems, the user has the choice between efficient predefined or configurable branching strategies reasoning on the scheduling objects, and the implementation of his own search heuristics.
The automated result display for scheduling problems (resource diagrams, Gantt charts) in the development environment IVE helps analyzing the obtained solutions.

Xpress-Kalis now also handles continuous variables and arithmetic (linear and non-linear) constraints over continuous and discrete variables. This means that mixed integer non-linear problems can now be solved with Xpress-Kalis.