tests/test_utils.py

+import pytest
+import sympy as sp
+from pystencils.utils import LinearEquationSystem
+from pystencils.utils import DotDict
+
+
+def test_linear_equation_system():
+    unknowns = sp.symbols("x_:3")
+    x, y, z = unknowns
+    m = LinearEquationSystem(unknowns)
+    m.add_equation(x + y - 2)
+    m.add_equation(x - y - 1)
+    assert m.solution_structure() == 'multiple'
+    m.set_unknown_zero(2)
+    assert m.solution_structure() == 'single'
+    solution = m.solution()
+    assert solution[unknowns[2]] == 0
+    assert solution[unknowns[1]] == sp.Rational(1, 2)
+    assert solution[unknowns[0]] == sp.Rational(3, 2)
+
+    m.set_unknown_zero(0)
+    assert m.solution_structure() == 'none'
+
+    # special case where less rows than unknowns, but no solution
+    m = LinearEquationSystem(unknowns)
+    m.add_equation(x - 3)
+    m.add_equation(x - 4)
+    assert m.solution_structure() == 'none'
+    m.add_equation(y - 4)
+    assert m.solution_structure() == 'none'
+
+    with pytest.raises(ValueError) as e:
+        m.add_equation(x**2 - 1)
+    assert 'Not a linear equation' in str(e.value)
+
+    x, y, z = sp.symbols("x, y, z")
+    les = LinearEquationSystem([x, y, z])
+    les.add_equation(1 * x + 2 * y - 1 * z + 4)
+    les.add_equation(2 * x + 1 * y + 1 * z - 2)
+    les.add_equation(1 * x + 2 * y + 1 * z + 2)
+
+    # usually reduce is not necessary since almost every function of LinearEquationSystem calls reduce beforehand
+    les.reduce()
+
+    expected_matrix = sp.Matrix([[1, 0, 0, sp.Rational(5, 3)],
+                                 [0, 1, 0, sp.Rational(-7, 3)],
+                                 [0, 0, 1, sp.Integer(1)]])
+    assert les.matrix == expected_matrix
+    assert les.rank == 3
+
+    sol = les.solution()
+    assert sol[x] == sp.Rational(5, 3)
+    assert sol[y] == sp.Rational(-7, 3)
+    assert sol[z] == sp.Integer(1)
+
+    les = LinearEquationSystem([x, y])
+    assert les.solution_structure() == 'multiple'
+
+    les.add_equation(x + 1)
+    assert les.solution_structure() == 'multiple'
+
+    les.add_equation(y + 2)
+    assert les.solution_structure() == 'single'
+
+    les.add_equation(x + y + 5)
+    assert les.solution_structure() == 'none'
+
+
+def test_dot_dict():
+    d = {'a': {'c': 7}, 'b': 6}
+    t = DotDict(d)
+    assert t.a.c == 7
+    assert t.b == 6
+    assert len(t) == 2
+
+    delattr(t, 'b')
+    assert len(t) == 1
+
+    t.b = 6
+    assert len(t) == 2
+    assert t.b == 6