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# XPRSstrongbranchcb

Purpose
Performs strong branching iterations on all specified bound changes. For each candidate bound change, XPRSstrongbranchcb performs dual simplex iterations starting from the current optimal solution of the base LP, and returns both the status and objective value reached after these iterations.
Topic area
Branching
Synopsis
`int XPRS_CC XPRSstrongbranchcb(XPRSprob prob, int nbounds, const int colind[], const char bndtype[], const double bndval[], int iterlim, double objval[], int status[], int (XPRS_CC *callback)(XPRSprob cbprob, void* cbdata, int bndidx), void* data);`
Arguments

prob | The current problem.
nbounds | Number of bound changes to try.
colind | Integer array of size nbounds containing the indices of the columns on which the bounds will change.
bndtype | Character array of length nbounds indicating the type of bound to change:
U | indicates change the upper bound;
L | indicates change the lower bound;
B | indicates change both bounds, i.e. fix the column.
bndval | Double array of length nbounds giving the new bound values.
iterlim | Maximum number of LP iterations to perform for each bound change.
objval | Array of objective values of each LP after performing the strong branching iterations.
status | Array of statuses of each LP after performing the strong branching iterations, as detailed for the LPSTATUS attribute.
callback | Function to be called after each strong branch has been reoptimized. This function returns an integer. Use 0 to indicate that everything went fine. Use a return value different from 0 to signal an error. This will terminate the function.
cbprob | The problem passed to the callback function, callback.
cbdata | The user-defined data passed as data.
bndidx | The index of the bound for which callback is called.
data | User context to be provided for callback.

Further information
This function currently does not apply to general nonlinear problems.
Prior to calling XPRSstrongbranchcb, the current LP problem must have been solved to optimality and an optimal basis must be available.
XPRSstrongbranchcb is an extension to XPRSstrongbranch. If identical input arguments are provided both will return identical results, the difference being that for the case of XPRSstrongbranchcb the callback function is called at the end of each LP reoptimization.
For each branch optimized, the LP can be interrogated: the LP status of the branch is available through checking LPSTATUS, and the objective function value is available through LPOBJVAL. It is possible to access the full current LP solution by using XPRSgetcallbacksolution.
The return value of callback function callback is currently ignored.
Parent Topic Console and Library Functions

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