Re: RE: [Help-glpk] The "dual" suffix and sensitivity to how a constraint is expressed in GMPL

[glpk xypron]

Hello Marc,

> Should GMPL be more clever and check if all the variables are only on
> one side of the constraint, and if so always place the variables on the
> left-side, and the constant on the right side, and not multiply by -1?
> That would create more intuitive dual variables.

A change in a logic will break existing programs relying on the
current sign.

For a constraint like

s.t. c{i in I} :
  sum{j in A[i]} x[j] <= sum{j n B[i]} x[j];

it would become quite non-intuitive to interprete the duals if 
some A[i] were empty.

Best regards

Xypron

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