Initializing help system before first use

# problem.getdualray

Purpose
This subroutine is deprecated and will be removed in a future release. Use problem.getDualRay instead.
Retrieves a dual ray (dual unbounded direction) for the current problem, if the problem is found to be infeasible.
Synopsis
`problem.getdualray(ray)`
Argument

ray | Array of length problem.attributes.rows to hold the ray. May be None if not required.

Example
The following code tries to retrieve a dual ray:

    if not p.hasdualray():
        print("Could not retrieve a dual ray")
    else:
        dray = []
        p.getdualray(dray)
        print("dual ray:", dray)

Further information
1. It is possible to retrieve a dual ray only when, after solving an LP problem, the final status is xpress.LPStatus.INFEAS.
2. Dual rays are not post-solved. If the problem is in a presolved state, the dual ray that is returned will be for the presolved problem. If the problem was solved with presolve on and has been restored to the original state (the default behavior), this function will not be able to return a ray. To ensure that a dual ray can be obtained, it is recommended to solve a problem with presolve turned off ( presolve = 0).
Related topics
problem.getPrimalRay, problem.getDualRay.
Parent Topic Deprecated functionality

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