CLP Extension of IBM Prolog

Appeared in Volume 7/1, February 1994

Keywords: constraints.

IBM intends to release a CLP extension of IBM Prolog, the result of research and development at the Paris Scientific Center. The main features of this product (name unknown at present) can be divided into two main categories:

1. It handles linear constraints over variables ranging over a continuous domain (namely R). In addition to the functionalities of CLP(R), "non-logical" predicates allowing maximization and control of the solver's algorithm are provided. One important feature of this real linear solver is that it is based on the revised simplex technology, often yielding much better performance than the tableau simplex used in other CLP systems.

2. It also handles constraints on variables ranging over an interval. These constraints (possibly non-linear) are solved using a domain reduction solver. The variables appearing in such constraints can take their values from two kinds of domains:

By default, the domain reduction solver handles variables ranging over real intervals. Using the default, means that an interval arithmetic solver is provided.
The user can also specify that a variable can only take values in a finite integer domain. To help the user model and solve hard combinatorial problems such as scheduling or allocation problems, several specialized constraints are provided.
Boolean constraints can also be handled using the domain reduction solver. A complete set of logical connectors is provided for such a purpose.

Specific methods are used depending on the type of variable the domain reduction algorithm is working on, thus allowing maximum performance while offering a simple, unified syntax.

The most important feature of this product is the integration of these constraint solvers so that problems with many types of constraints can be solved. This integration goes further than any other CLP language because mixed constraints are allowed. For example, variables appearing in a domain reduction constraint can also be used in constraints solved by the Simplex algorithm. This yields a whole new set of applications for CLP languages.

The product should be available on OS/2 by February 1994.

For more information please contact:

Henri Beringer or Bruno De Backer
IBM Scientific Center
68/76 Quai de la Rapee
75592 Paris Cedex 12, France
Email: beringer@vnet.ibm.com,
       bdb@vnet.ibm.com
Tel: +33 1 4001 5257 or 5361