Duaffle version 1.0NL
Cornell University, 2007

April 10, 2007

This package contains the QBF solver Duaffle version 1.0NL (without
learning), which uses a dual-format "cnfdnf" file as input. This file
contains a set of traditional CNF clauses as well as a set of DNF
terms. See example.qdimacs for an example of such a file. The syntax
is essentially the same as the standard QDIMACS format for QBF, except
that the header line looks like 

  p cnfdnf <operator> <n_var> <n_cl> <n_terms>

and the constraints are divided into two parts separated by a line
containing only a zero. The first part has CNF constraints as a set of
clauses while the second part has DNF constraints as a set of terms.
Semantically they are joined together using the logical operator
specified in the header, which is either "or" or "and". Lines
beginning with a 'c' are treated as comments as usual.

NOTICE: THIS CODE IS STILL UNDER PROGRESS AND DOES NOT HAVE CLAUSE-
AND SOLUTION-LEARNING ENABLED!! Nonetheless, it often performs quite
well compared to other state-of-the-art QBF solvers. See, e.g.,
results published in the above paper.

COMPILATION: 
  Type "make" to compile using g++; this will create an executable
  called duaffle.

USAGE: 
  The usage is same as that of its parent QBF solver, Quaffle:

     duaffle cnfdnf_file [optional time_limit in seconds]

USAGE EXAMPLE:
     duaffle example.qdimacs

This will evaluate the input dual-format QBF formula and output QSAT
or QUNSAT depending on the result. In addition, when QSAT, it will
also output the values of the variables in the first existential layer
that were found to lead to a consistent solution. This solution
printing may be turned off by commenting out the corresponding line in
the file config.h and recompiling.

For further details, please see the paper "QBF Modeling: Exploiting
Player Symmetry for Simplicity and Efficiency" in the proceedings of
SAT-06 (also available from http://www.cs.cornell.edu/~sabhar).

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Please report bugs and send comments/questions to
  Ashish Sabharwal, sabhar at cs dot cornell dot edu.

