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setcallback

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Purpose

Set optimizer callback functions and procedures.

Synopsis

procedure setcallback(cbtype:integer, cb:string)

Arguments

cbtype

Type of the callback: XPRS_CB_LPLOG  Simplex log callback XPRS_CB_CUTLOG  Cut log callback XPRS_CB_GLOBALLOG  Global log callback XPRS_CB_BARLOG  Barrier log callback XPRS_CB_CHGNODE  User select node callback XPRS_CB_PRENODE  User preprocess node callback XPRS_CB_OPTNODE  User optimal node callback XPRS_CB_INFNODE  User infeasible node callback XPRS_CB_INTSOL  User integer solution callback XPRS_CB_NODECUTOFF  User cut-off node callback XPRS_CB_INITCUTMGR  Cut manager initialization callback XPRS_CB_FREECUTMGR  Cut manager termination callback XPRS_CB_CUTMGR  Cut manager (branch-and-bound node) callback XPRS_CB_CHGBRANCH  User choose branching variable callback

cb

Name of the callback function/procedure; the parameters and the type of the return value (if any) vary depending on the type of the callback: function cb:boolean  XPRS_CB_LPLOG function cb:boolean  XPRS_CB_CUTLOG function cb:boolean  XPRS_CB_GLOBALLOG function cb:boolean  XPRS_CB_BARLOG function cb(node:integer):integer  XPRS_CB_CHGNODE function cb(node:integer):integer  XPRS_CB_PRENODE function cb:boolean  XPRS_CB_OPTNODE procedure cb  XPRS_CB_INFNODE procedure cb  XPRS_CB_INTSOL procedure cb(node:integer)  XPRS_CB_NODECUTOFF procedure cb  XPRS_CB_INITCUTMGR procedure cb  XPRS_CB_FREECUTMGR function cb:boolean  XPRS_CB_CUTMGR procedure cb(e:integer,u:integer,d:real)  XPRS_CB_CHGBRANCH

Example

The following example defines a procedure to handle solution printing and sets it to be called whenever an integer solution is found using the integer solution callback:

procedure printsol
 declarations
  objval:real
 end-declarations

 objval:= getparam("XPRS_lpobjval")
 writeln("Solution value: ", objval)
end-procedure
	
setcallback(XPRS_CB_INTSOL, "printsol") 

Further information

This procedure sets the optimizer callback functions and procedures. Passing an empty string ("") as the function name disables the corresponding callback. For a detailed description of these callbacks the user is referred to the Xpress-Optimizer Reference Manual. Note that whilst the solution values can be accessed from Mosel in any callback function/procedure, all other information such as the problem status or the value of the objective function must be obtained directly from the Optimizer using function getparam. Note further that the function setucbdata can be used to return information to the optimizer from the callback `CHGBRANCH'.

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