satisfy_openmp


satisfy_openmp, a Fortran90 code which demonstrates, for a particular circuit, an exhaustive search for solutions of the circuit satisfy problem, using OpenMP for parallel execution.

This problem assumes that we are given a logical circuit of AND, OR and NOT gates, with N=23 binary inputs and a single output. We are to determine all inputs which produce a 1 as the output.

The general problem is NP complete, so there is no known polynomial-time algorithm to solve the general case. The natural way to search for solutions then is exhaustive search of all 2^N possible inputs.

In an interesting way, this is a very extreme and discrete version of the problem of maximizing a scalar function of multiple variables. The difference is that here we know that both the input and output only have the values 0 and 1, rather than a continuous range of real values!

This problem is a natural candidate for parallel computation, since the individual evaluations of the circuit are completely independent.

On an Apple PowerPC G5 with two processors, the following results were observed:
Threads2^NTime
18,388,6084.38 seconds
28,388,6082.29 seconds
48,388,6082.29 seconds

Usage:

In the BASH shell, the program could be run with 2 threads using the commands:

        export OMP_NUM_THREADS=2
        ./satisfy_openmp
      

Licensing:

The information on this web page is distributed under the MIT license.

Languages:

satisfy_openmp is available in a C version and a C++ version and a Fortran90 version.

Related Data and Programs:

satisfy_openmp_test

openmp_test, a Fortran90 code which uses the OpenMP application code interface for carrying out parallel computations in a shared memory environment.

satisfy_brute, a Fortran90 code which demonstrates, for a particular circuit, an exhaustive search for solutions of the circuit satisfy problem.

Reference:

  1. Michael Quinn,
    Parallel Programming in C with MPI and OpenMP,
    McGraw-Hill, 2004,
    ISBN13: 978-0071232654,
    LC: QA76.73.C15.Q55.

Source Code:


Last revised on 05 August 2020.