void __declspec(dllexport) WINAPI _set_lag_trace(lprec *lp, long lag_trace)
{
if (lp != NULL) {
freebuferror();
set_lag_trace(lp, (MYBOOL) lag_trace);
}
}
int main(void)
{
# if defined ERROR
# undef ERROR
# endif
# define ERROR() { fprintf(stderr, "Error\n"); exit(1); }
lprec *lp;
int majorversion, minorversion, release, build;
#if defined FORTIFY
Fortify_EnterScope();
#endif
lp_solve_version(&majorversion, &minorversion, &release, &build);
printf("lp_solve %d.%d.%d.%d demo\n\n", majorversion, minorversion, release, build);
printf("This demo will show most of the features of lp_solve %d.%d.%d.%d\n", majorversion, minorversion, release, build);
press_ret();
printf("\nWe start by creating a new problem with 4 variables and 0 constraints\n");
printf("We use: lp=make_lp(0,4);\n");
if ((lp=make_lp(0,4)) == NULL)
ERROR();
press_ret();
printf("We can show the current problem with print_lp(lp)\n");
print_lp(lp);
press_ret();
printf("Now we add some constraints\n");
printf("str_add_constraint(lp, \"3 2 2 1\" ,LE,4)\n");
printf("This is the string version of add_constraint. For the normal version\n");
printf("of add_constraint see the help file\n");
if (!str_add_constraint(lp, "3 2 2 1", LE, 4))
ERROR();
print_lp(lp);
press_ret();
printf("str_add_constraint(lp, \"0 4 3 1\" ,GE,3)\n");
if (!str_add_constraint(lp, "0 4 3 1", GE, 3))
ERROR();
print_lp(lp);
press_ret();
printf("Set the objective function\n");
printf("str_set_obj_fn(lp, \"2 3 -2 3\")\n");
if (!str_set_obj_fn(lp, "2 3 -2 3"))
ERROR();
print_lp(lp);
press_ret();
printf("Now solve the problem with printf(solve(lp));\n");
printf("%d",solve(lp));
press_ret();
printf("The value is 0, this means we found an optimal solution\n");
printf("We can display this solution with print_objective(lp) and print_solution(lp)\n");
print_objective(lp);
print_solution(lp, 1);
print_constraints(lp, 1);
press_ret();
printf("The dual variables of the solution are printed with\n");
printf("print_duals(lp);\n");
print_duals(lp);
press_ret();
printf("We can change a single element in the matrix with\n");
printf("set_mat(lp,2,1,0.5)\n");
if (!set_mat(lp,2,1,0.5))
ERROR();
print_lp(lp);
press_ret();
printf("If we want to maximize the objective function use set_maxim(lp);\n");
set_maxim(lp);
print_lp(lp);
press_ret();
printf("after solving this gives us:\n");
solve(lp);
print_objective(lp);
print_solution(lp, 1);
print_constraints(lp, 1);
print_duals(lp);
press_ret();
printf("Change the value of a rhs element with set_rh(lp,1,7.45)\n");
set_rh(lp,1,7.45);
print_lp(lp);
solve(lp);
print_objective(lp);
print_solution(lp, 1);
print_constraints(lp, 1);
press_ret();
printf("We change %s to the integer type with\n", get_col_name(lp, 4));
printf("set_int(lp, 4, TRUE)\n");
set_int(lp, 4, TRUE);
print_lp(lp);
printf("We set branch & bound debugging on with set_debug(lp, TRUE)\n");
set_debug(lp, TRUE);
printf("and solve...\n");
press_ret();
solve(lp);
print_objective(lp);
print_solution(lp, 1);
print_constraints(lp, 1);
press_ret();
printf("We can set bounds on the variables with\n");
printf("set_lowbo(lp,2,2); & set_upbo(lp,4,5.3)\n");
set_lowbo(lp,2,2);
set_upbo(lp,4,5.3);
print_lp(lp);
press_ret();
solve(lp);
print_objective(lp);
print_solution(lp, 1);
print_constraints(lp, 1);
press_ret();
printf("Now remove a constraint with del_constraint(lp, 1)\n");
del_constraint(lp,1);
print_lp(lp);
printf("Add an equality constraint\n");
if (!str_add_constraint(lp, "1 2 1 4", EQ, 8))
ERROR();
print_lp(lp);
press_ret();
printf("A column can be added with:\n");
printf("str_add_column(lp,\"3 2 2\");\n");
if (!str_add_column(lp,"3 2 2"))
ERROR();
print_lp(lp);
press_ret();
printf("A column can be removed with:\n");
printf("del_column(lp,3);\n");
del_column(lp,3);
print_lp(lp);
press_ret();
printf("We can use automatic scaling with:\n");
printf("set_scaling(lp, SCALE_MEAN);\n");
set_scaling(lp, SCALE_MEAN);
print_lp(lp);
press_ret();
printf("The function get_mat(lprec *lp, int row, int column) returns a single\n");
printf("matrix element\n");
printf("%s get_mat(lp,2,3), get_mat(lp,1,1); gives\n","printf(\"%f %f\\n\",");
printf("%f %f\n", (double)get_mat(lp,2,3), (double)get_mat(lp,1,1));
printf("Notice that get_mat returns the value of the original unscaled problem\n");
press_ret();
printf("If there are any integer type variables, then only the rows are scaled\n");
printf("set_int(lp,3,FALSE);\n");
printf("set_scaling(lp, SCALE_MEAN);\n");
set_scaling(lp, SCALE_MEAN);
set_int(lp,3,FALSE);
print_lp(lp);
press_ret();
solve(lp);
printf("print_objective, print_solution gives the solution to the original problem\n");
print_objective(lp);
print_solution(lp, 1);
print_constraints(lp, 1);
press_ret();
printf("Scaling is turned off with unscale(lp);\n");
unscale(lp);
print_lp(lp);
press_ret();
printf("Now turn B&B debugging off and simplex tracing on with\n");
printf("set_debug(lp, FALSE), set_trace(lp, TRUE) and solve(lp)\n");
set_debug(lp, FALSE);
set_trace(lp, TRUE);
press_ret();
solve(lp);
printf("Where possible, lp_solve will start at the last found basis\n");
printf("We can reset the problem to the initial basis with\n");
printf("default_basis(lp). Now solve it again...\n");
press_ret();
default_basis(lp);
solve(lp);
printf("It is possible to give variables and constraints names\n");
printf("set_row_name(lp,1,\"speed\"); & set_col_name(lp,2,\"money\")\n");
if (!set_row_name(lp,1,"speed"))
ERROR();
if (!set_col_name(lp,2,"money"))
ERROR();
print_lp(lp);
printf("As you can see, all column and rows are assigned default names\n");
printf("If a column or constraint is deleted, the names shift place also:\n");
press_ret();
printf("del_column(lp,1);\n");
del_column(lp,1);
print_lp(lp);
press_ret();
delete_lp(lp);
#if FALSE
printf("A lp structure can be created and read from a .lp file\n");
printf("lp = read_lp(\"lp_examples/demo_lag.lp\", TRUE);\n");
printf("The verbose option is used\n");
if ((lp = read_LP("lp_examples/demo_lag.lp", TRUE, "test")) == NULL)
ERROR();
press_ret();
printf("lp is now:\n");
print_lp(lp);
press_ret();
printf("solution:\n");
set_debug(lp, TRUE);
solve(lp);
set_debug(lp, FALSE);
print_objective(lp);
print_solution(lp, 1);
print_constraints(lp, 1);
press_ret();
printf("You can see that branch & bound was used in this problem\n");
printf("Now remove the last constraint and use lagrangian relaxation\n");
printf("del_constraint(lp,6);\n");
printf("str_add_lag_con(lp, \"1 1 1 0 0 0\", LE, 2);\n");
del_constraint(lp,6);
if (!str_add_lag_con(lp, "1 1 1 0 0 0", LE, 2))
ERROR();
print_lp(lp);
printf("Lagrangian relaxation is used in some heuristics. It is now possible\n");
printf("to get a feasible integer solution without usage of branch & bound.\n");
printf("Use lag_solve(lp, 0, 30); 0 is the initial bound, 30 the maximum\n");
printf("number of iterations, the last variable turns the verbose mode on.\n");
press_ret();
set_lag_trace(lp, TRUE);
printf("%d\n",lag_solve(lp, 0, 30));
printf("The returncode of lag_solve is 6 or FEAS_FOUND. this means that a feasible\n");
printf("solution has been found. For a list of other possible return values\n");
printf("see the help file. Print this solution with print_objective, print_solution\n");
print_objective(lp);
print_solution(lp, 1);
print_constraints(lp, 1);
delete_lp(lp);
press_ret();
#endif
#if defined FORTIFY
Fortify_LeaveScope();
#endif
return(0);
}
