problem.chgdf
problem.chgdf |
Purpose
Set or change a distribution factor
Synopsis
problem.chgdf(colindex, rowindex, value)
Arguments
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colindex
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The column (i.e.
xpress.var object, index, or name) whose distribution factor is to be set or changed.
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rowindex
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The row (i.e.
xpress.constraint object, index, or name) where the distribution applies.
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value
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Address of a double precision variable holding the new value of the distribution factor. May be
None if not required.
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Example
The following example retrieves the value of the distribution factor for column 282 in row 134 and changes it to be twice as large.
value = p.getdf(282,134) value *= 2 p.chgdf(282,134,value)
Further information
The distribution factor of a column in a row is the matrix coefficient of the corresponding delta vector in the row. Distribution factors are used in conventional recursion models, and are essentially normalized first-order derivatives. Xpress Nonlinear can accept distribution factors instead of initial values, provided that the values of the variables involved can all be calculated after optimization using determining rows, or by a callback.
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