static int CPXPUBLIC
usersolve (CPXCENVptr env,
void *cbdata,
int wherefrom,
void *cbhandle,
int *useraction_p)
{
int status = 0;
CPXCNT nodecount;
CPXLPptr nodelp;
*useraction_p = CPX_CALLBACK_DEFAULT;
/* Get pointer to LP subproblem */
status = CPXXgetcallbacknodelp (env, cbdata, wherefrom, &nodelp);
if ( status ) goto TERMINATE;
/* Find out what node is being processed */
status = CPXXgetcallbackinfo (env, cbdata, wherefrom,
CPX_CALLBACK_INFO_NODE_COUNT_LONG,
&nodecount);
if ( status ) goto TERMINATE;
/* Solve initial node with primal, others with dual */
if ( nodecount < 1 ) status = CPXXprimopt (env, nodelp);
else status = CPXXdualopt (env, nodelp);
/* If the solve was OK, set return to say optimization has
been done in callback, otherwise return the CPLEX error
code */
if ( !status ) *useraction_p = CPX_CALLBACK_SET;
TERMINATE:
return (status);
} /* END usersolve */
static int CPXPUBLIC
solvecallback (CPXCENVptr env,
void *cbdata,
int wherefrom,
void *userinfo,
int *useraction_p)
{
int status = 0;
int lpstatus = 0;
CPXLPptr nodelp = NULL;
double *prex = NULL;
MYCBptr mycbinfo = (MYCBptr) userinfo;
CPXLPptr mip = mycbinfo->mip;
double *relx = mycbinfo->relx;
CPXDIM cols;
int prestat;
*useraction_p = CPX_CALLBACK_DEFAULT;
/* Only use callback for solving the root relaxation (node 0) */
if ( mycbinfo->count > 0 ) {
goto TERMINATE;
}
mycbinfo->count++;
/* Extract the LP to be solved */
status = CPXXgetcallbacknodelp (env, cbdata, wherefrom, &nodelp);
if ( status ) goto TERMINATE;
cols = CPXXgetnumcols (env, nodelp);
prex = malloc (cols * sizeof (*prex));
if ( prex == NULL ) {
status = CPXERR_NO_MEMORY;
goto TERMINATE;
}
/* Use MIP presolve to crush the original solution. Note that
MIP presolve can only crush primal solutions */
status = CPXXgetprestat (env, mip, &prestat, NULL, NULL, NULL,
NULL);
if ( status ) goto TERMINATE;
/* If a presolved model exists, then relx is crushed down
to prex, the corresponding solution for the presolved
model; otherwise, prex is just a copy of relx */
if ( prestat ) {
status = CPXXcrushx (env, mip, relx, prex);
if ( status ) goto TERMINATE;
}
else {
memcpy (prex, relx, cols * sizeof (*relx));
}
/* Feed the crushed solution into 'nodelp' */
status = CPXXcopystart (env, nodelp, NULL, NULL, prex, NULL,
NULL, NULL);
/* Use primal to reoptimize, since we only have a primal
solution */
status = CPXXprimopt (env, nodelp);
if ( status ) goto TERMINATE;
lpstatus = CPXXgetstat (env, nodelp);
if ( lpstatus == CPX_STAT_OPTIMAL ||
lpstatus == CPX_STAT_OPTIMAL_INFEAS ||
lpstatus == CPX_STAT_INFEASIBLE ) {
*useraction_p = CPX_CALLBACK_SET;
}
TERMINATE:
free_and_null ((char **) &prex);
return (status);
} /* END solvecallback */