add OrthogonalBlock to make input orthonormal

tests/test_layers/test_orthogonal.py

@@ -0,0 +1,33 @@
+import torch
+import pytest
+from pina.model.layers.orthogonal import OrthogonalBlock
+
+list_matrices = [
+    torch.randn(10, 3),
+    torch.rand(100, 5),
+    torch.randn(5, 5),
+    ]
+
+list_prohibited_matrices_dim0 = list_matrices[:-1]
+
+def test_constructor():
+    orth = OrthogonalBlock(1) 
+    orth = OrthogonalBlock(0) 
+    orth = OrthogonalBlock()
+
+@pytest.mark.parametrize("V", list_matrices)
+def test_forward(V):
+    orth = OrthogonalBlock()
+    orth_row = OrthogonalBlock(0)
+    V_orth = orth(V)
+    V_orth_row = orth_row(V.T)
+    assert torch.allclose(V_orth.T @ V_orth, torch.eye(V.shape[1]), atol=1e-6)
+    assert torch.allclose(V_orth_row @ V_orth_row.T, torch.eye(V.shape[1]), atol=1e-6)
+
+@pytest.mark.parametrize("V", list_prohibited_matrices_dim0)
+def test_forward_prohibited(V):
+    orth = OrthogonalBlock(0)
+    with pytest.raises(Warning):
+        V_orth = orth(V)
+        assert V.shape[0] > V.shape[1]
+