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#include <assert.h>
#include <glpk.h>
#include <iostream>
#include "cpu_time.h"
#include "linprog/glpk.h"
class GLPKSolution : public Solution
{
private:
glp_prob *glpk;
const LinearProgram &linprog;
const unsigned int num_cols;
const unsigned int num_rows;
unsigned int num_coeffs;
bool solved;
void solve(double var_lb, double var_ub);
void set_objective();
void set_bounds(double col_lb, double col_ub);
void set_coefficients();
public:
GLPKSolution(const LinearProgram &lp, unsigned int max_num_vars,
double var_lb = 0.0, double var_ub = 1.0);
~GLPKSolution();
double get_value(unsigned int var) const
{
return glp_get_col_prim(glpk, var + 1);
}
bool is_solved() const
{
return solved;
}
};
GLPKSolution::GLPKSolution(const LinearProgram& lp, unsigned int max_num_vars,
double var_lb, double var_ub)
: glpk(glp_create_prob()),
linprog(lp),
num_cols(max_num_vars),
num_rows(lp.get_equalities().size() +
lp.get_inequalities().size()),
num_coeffs(0),
solved(false)
{
if (num_cols)
solve(var_lb, var_ub);
else
// Trivial case: no variables.
// This can happen if a task set does not
// contain any shared resources.
solved = true;
}
void GLPKSolution::solve(double var_lb, double var_ub)
{
#if DEBUG_LP_OVERHEADS >= 3
static DEFINE_CPU_CLOCK(init_costs);
static DEFINE_CPU_CLOCK(model_costs);
static DEFINE_CPU_CLOCK(solver_costs);
init_costs.start();
#endif
glp_term_out(GLP_OFF);
glp_set_obj_dir(glpk, GLP_MAX);
glp_add_cols(glpk, num_cols);
glp_add_rows(glpk, num_rows);
#if DEBUG_LP_OVERHEADS >= 3
init_costs.stop();
model_costs.start();
#endif
set_objective();
set_bounds(var_lb, var_ub);
set_coefficients();
#if DEBUG_LP_OVERHEADS >= 3
model_costs.stop();
solver_costs.start();
#endif
glp_smcp glpk_params;
glp_init_smcp(&glpk_params);
/* Set solver options. The presolver is essential. The other two
* options seem to make the solver slightly faster.
*
* Tested with GLPK 4.43 on wks-50-12.
*/
glpk_params.presolve = GLP_ON;
glpk_params.pricing = GLP_PT_STD;
glpk_params.r_test = GLP_RT_STD;
solved = glp_simplex(glpk, &glpk_params) == 0 &&
glp_get_status(glpk) == GLP_OPT;
#if DEBUG_LP_OVERHEADS >= 3
solver_costs.stop();
std::cout << init_costs << std::endl
<< model_costs << std::endl
<< solver_costs << std::endl;
#endif
}
GLPKSolution::~GLPKSolution()
{
glp_delete_prob(glpk);
}
void GLPKSolution::set_objective()
{
assert(linprog.get_objective()->get_terms().size() <= num_cols);
foreach (linprog.get_objective()->get_terms(), term)
glp_set_obj_coef(glpk, term->second + 1, term->first);
}
void GLPKSolution::set_bounds(double col_lb, double col_ub)
{
unsigned int r = 1;
foreach(linprog.get_equalities(), equ)
{
glp_set_row_bnds(glpk, r++, GLP_FX,
equ->second, equ->second);
num_coeffs += equ->first->get_terms().size();
}
foreach(linprog.get_inequalities(), inequ)
{
glp_set_row_bnds(glpk, r++, GLP_UP,
0, inequ->second);
num_coeffs += inequ->first->get_terms().size();
}
for (unsigned int c = 1; c <= num_cols; c++)
glp_set_col_bnds(glpk, c, GLP_DB, col_lb, col_ub);
}
void GLPKSolution::set_coefficients()
{
int *row_idx, *col_idx;
double *coeff;
row_idx = new int[1 + num_coeffs];
col_idx = new int[1 + num_coeffs];
coeff = new double[1 + num_coeffs];
unsigned int r = 1, k = 1;
foreach(linprog.get_equalities(), equ)
{
foreach(equ->first->get_terms(), term)
{
assert(k <= num_coeffs);
row_idx[k] = r;
col_idx[k] = 1 + term->second;
coeff[k] = term->first;
k += 1;
}
r += 1;
}
foreach(linprog.get_inequalities(), inequ)
{
foreach(inequ->first->get_terms(), term)
{
assert(k <= num_coeffs);
row_idx[k] = r;
col_idx[k] = 1 + term->second;
coeff[k] = term->first;
k += 1;
}
r += 1;
}
glp_load_matrix(glpk, num_coeffs, row_idx, col_idx, coeff);
delete[] row_idx;
delete[] col_idx;
delete[] coeff;
}
Solution *glpk_solve(const LinearProgram& lp, unsigned int max_num_vars)
{
GLPKSolution *sol = new GLPKSolution(lp, max_num_vars);
if (sol->is_solved())
return sol;
else
{
delete sol;
return NULL;
}
}
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