// Maximize a + b subject to both 0 ≤ 2a + b ≤ 10 and 3 ≤ 2b − a ≤ 8.
func ExampleSimplex_LoadProblem() {
// Set up the problem.
mat := clp.NewPackedMatrix()
mat.AppendColumn([]clp.Nonzero{
{Index: 0, Value: 2.0}, // 2a
{Index: 1, Value: -1.0}, // -a
})
mat.AppendColumn([]clp.Nonzero{
{Index: 0, Value: 1.0}, // b
{Index: 1, Value: 2.0}, // 2b
})
rb := []clp.Bounds{
{Lower: 0, Upper: 10}, // [0, 10]
{Lower: 3, Upper: 8}, // [3, 8]
}
obj := []float64{1.0, 1.0} // a + b
simp := clp.NewSimplex()
simp.LoadProblem(mat, nil, obj, rb, nil)
simp.SetOptimizationDirection(clp.Maximize)
// Solve the optimization problem.
simp.Primal(clp.NoValuesPass, clp.NoStartFinishOptions)
val := simp.ObjectiveValue()
soln := simp.PrimalColumnSolution()
// Output the results.
fmt.Printf("a = %.1f\nb = %.1f\na + b = %.1f\n", soln[0], soln[1], val)
// Output:
// a = 2.4
// b = 5.2
// a + b = 7.6
}
// Test if we can solve a complete optimization problem with the simplex model.
func TestPrimalSolve(t *testing.T) {
// Set up the following problem: Minimize a + 2b subject to {4 ≤ a + b
// ≤ 9, -5 ≤ 3a − b ≤ 3}.
mat := clp.NewPackedMatrix()
mat.AppendColumn([]clp.Nonzero{
{Index: 0, Value: 1.0}, // a
{Index: 1, Value: 3.0}, // 3a
})
mat.AppendColumn([]clp.Nonzero{
{Index: 0, Value: 1.0}, // b
{Index: 1, Value: -1.0}, // -b
})
rb := []clp.Bounds{
{Lower: 4, Upper: 9}, // [4, 9]
{Lower: -5, Upper: 3}, // [-5, 3]
}
obj := []float64{1.0, 2.0} // a + 2b
simp := clp.NewSimplex()
simp.LoadProblem(mat, nil, obj, rb, nil)
simp.SetOptimizationDirection(clp.Minimize)
// Solve the optimization problem.
simp.Primal(clp.NoValuesPass, clp.NoStartFinishOptions)
v := simp.ObjectiveValue()
soln := simp.PrimalColumnSolution()
// Check the results.
if !closeTo(soln[0], 1.75, 0.005) || !closeTo(soln[1], 2.25, 0.005) {
t.Fatalf("Expected [1.75 2.25] but observed %v", soln)
}
if !closeTo(v, 6.25, 0.005) {
t.Fatalf("Expected 6.25 but observed %.10g", v)
}
}
// Test if we can add columns to a packed matrix and get the expected dump in
// return.
func TestDumpMatrix(t *testing.T) {
m := clp.NewPackedMatrix()
addColumns(m, 5, 5)
expected := `Dumping matrix...
colordered: 1
major: 5 minor: 5
vec 0 has length 2 with entries:
0 0.0000000000000000000000000
4 -0.0000000000000000000000000
vec 1 has length 2 with entries:
1 10.0000000000000000000000000
3 -10.0000000000000000000000000
vec 2 has length 2 with entries:
2 20.0000000000000000000000000
2 -20.0000000000000000000000000
vec 3 has length 2 with entries:
3 30.0000000000000000000000000
1 -30.0000000000000000000000000
vec 4 has length 2 with entries:
4 40.0000000000000000000000000
0 -40.0000000000000000000000000
Finished dumping matrix
`
var buf bytes.Buffer
m.DumpMatrix(&buf)
actual := buf.String()
if actual != expected {
t.Logf("Expected output follows:\n%s", expected)
t.Logf("Actual output follows:\n%s", actual)
t.Fatalf("Mismatch between expected and actual matrix contents")
}
}
// Test if we can query a packed matrix's dimensions.
func TestDims(t *testing.T) {
for _, trials := range [...][2]int{
{66, 7}, // Wide
{55, 68}, // Tall
} {
nr, nc := trials[0], trials[1]
m := clp.NewPackedMatrix()
addColumns(m, nr, nc)
r, c := m.Dims()
if r != nr || c != nc {
t.Fatalf("Expected %dx%d but saw %dx%d", nr, nc, r, c)
}
}
}
// Test if we can load a problem into a simplex model.
func TestLoadProblem(t *testing.T) {
s := clp.NewSimplex()
m := clp.NewPackedMatrix()
s.LoadProblem(m, nil, nil, nil, nil)
}
// Test if we can add columns to a packed matrix.
func TestAddColumns(t *testing.T) {
m := clp.NewPackedMatrix()
addColumns(m, 1000, 1000)
}
// Test if we can create a packed matrix.
func TestCreateMatrix(t *testing.T) {
_ = clp.NewPackedMatrix()
}