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# XSLPsetcbcascadevar, XPRSsetcbslpcascadevar

Purpose
Set a user callback to be called after each column has been cascaded
Topic areas
Callback, SLP, Cascading
Synopsis
`int XPRS_CC XSLPsetcbcascadevar(XSLPprob prob, int (XPRS_CC *cascadevar) (XSLPprob cbprob, void *cbdata, int col), void *data);`
Arguments

prob | The current SLP problem.
cascadevar | The function to be called after each column has been cascaded. cascadevar returns an integer value. If the return value is nonzero, the cascading process will be omitted for the remaining variables during the current SLP iteration, but the optimization will continue.
cbprob | The problem passed to the callback function.
cbdata | The user-defined object passed as data to XSLPsetcbcascadevar.
col | The number of the column which has been cascaded.
data | A user-defined object, which can be used for any purpose by the function. data is passed to cascadevar as cbdata.

Example
The following example sets up a callback to be executed after each variable has been cascaded:

    double *cSol;
    XSLPsetcbcascadevar(prob, CBCascVar, &cSol);

The following sample callback function resets the value of the variable if the cascaded value is of the opposite sign to the original value:

    int XPRS_CC CBCascVar(XSLPprob MyProb, void *Obj, int iCol) {
      double *cSol, Value;
      cSol = * (double **) Obj;
      XSLPgetvar(MyProb, iCol, NULL, NULL, NULL,
                 NULL, NULL, NULL, &Value,
                 NULL, NULL, NULL, NULL,
                 NULL, NULL, NULL, NULL);
      if (Value * cSol[iCol] < 0) {
        Value = cSol[iCol];
        XSLPchgvar(MyProb, ColNum, NULL, NULL, NULL, NULL,
                   NULL, NULL, &Value, NULL, NULL, NULL,
                   NULL);
      }
      return 0;
    }

The data argument is used here to hold the address of the array cSol which we assume has been populated with the original solution values.
Further information
This callback can be used after each variable has been cascaded and its new value has been calculated.
Related topics
XSLPcascade, XSLPsetcbcascadeend, XSLPsetcbcascadestart, XSLPsetcbcascadevarfail
Parent Topic Library functions and the programming interface

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