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); }