Factorable Programming for PWL Approximations

[michaelbynum]

Summary/Motivation:

The purpose of this module/transformation is to convert any nonlinear model
to the following form:

min/max e(x_i)*f(x_j) + b^T*x
s.t.
        g_j(x_i)*h_j(x_k) + a_j^T*x >/</== 0
        g_j(x_i)/h_j(x_k) + a_j^T*x >/</== 0
        g_j(x_i)**h_j(x_k) + a_j^T*x >/</== 0

By doing so, each nonlinear function is only a function of one or two variables.
If this transformation is used prior to the nonlinear_to_pwl transformation,
it can, in some cases, significantly reduce the complexity of the PWL approximation.

Legal Acknowledgement

By contributing to this software project, I have read the contribution guide and agree to the following terms and conditions for my contribution:

1. I agree my contributions are submitted under the BSD license.
2. I represent I am authorized to make the contributions and grant the license. If my employer has rights to intellectual property that includes these contributions, I represent that I have received permission to make contributions and grant the required license on behalf of that employer.