From ccb04a8dced03d28ffc01df0d06a704ecfbeee2a Mon Sep 17 00:00:00 2001
From: Ali-Tehrani <alirezatehrani24@gmail.com>
Date: Fri, 31 Jul 2020 19:12:31 -0400
Subject: [PATCH] Add tests for conversion vecs wrt basis sets

---
 iodata/test/test_overlap.py | 78 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 77 insertions(+), 1 deletion(-)

diff --git a/iodata/test/test_overlap.py b/iodata/test/test_overlap.py
index f1829886..ae80c2ee 100644
--- a/iodata/test/test_overlap.py
+++ b/iodata/test/test_overlap.py
@@ -24,8 +24,9 @@
 
 from ..api import load_one
 from ..basis import MolecularBasis, Shell
-from ..overlap import compute_overlap, OVERLAP_CONVENTIONS
+from ..overlap import compute_overlap, OVERLAP_CONVENTIONS, convert_vector_basis
 from ..overlap_accel import fac2, _binom
+from ..overlap_cartpure import tfs
 
 try:
     from importlib_resources import path
@@ -107,3 +108,78 @@ def test_overlap_l1():
     atcoords = np.zeros((3, 1))
     with raises(ValueError):
         _ = compute_overlap(dbasis, atcoords)
+
+
+def test_converting_between_orthonormal_basis_set():
+    # Test converting from basis set of M Elements to N Elements where M <= N.
+    # All basis sets are assumed orthonormal and 1st basis set is assumed to be
+    # in the second basis set.
+    M = np.random.randint(1, 25)
+    N = np.random.randint(M, 50)
+    coeffs1 = np.random.random(M)
+    basis2_overlap = np.eye(N)  # Since it is orthonormal, it is identity.
+
+    basis21_overlap = np.zeros((N, M))
+    for i in range(0, M):
+        basis21_overlap[i, i] = 1.  # Since it is a subset.
+
+    coeffs2 = convert_vector_basis(coeffs1, basis2_overlap, basis21_overlap)
+    assert_equal(coeffs1, coeffs2[:M])
+    assert_equal(np.zeros(coeffs2[M:].shape), coeffs2[M:])
+
+    # Test converting in the reverse direction ie Large to small.
+    coeffs2 = np.random.random(N)
+    basis1_overlap = np.eye(M)
+    basis12_overlap = np.zeros((M, N))
+    for i in range(0, M):
+        basis12_overlap[i, i] = 1.  # Since it is a subset.
+
+    coeffs1 = convert_vector_basis(coeffs2, basis1_overlap, basis12_overlap)
+    assert_equal(len(coeffs1), M)
+    assert_equal(coeffs1, coeffs2[:M])
+
+
+def test_converting_from_cartesian_to_pure():
+    # Test converting simple one coefficient, S-type.
+    overlap_cp = tfs[0]
+    coeff = np.array([5.])
+    coeff2 = convert_vector_basis(coeff, np.eye(1), overlap_cp)
+    assert_equal(coeff, coeff2)
+
+    # Test converting p-type.
+    overlap_cp = tfs[1]
+    coeff = np.array([1., 2., 3.])
+    coeff2 = convert_vector_basis(coeff, np.eye(3), overlap_cp)
+    desired = np.array([3., 1., 2.])
+    assert_equal(coeff2, desired)
+
+    # Test converting d-type.
+    overlap_cp = tfs[2]
+    coeff = np.array([1.0, 2.0, 3.0, 4.0, 5.0, 6.0])
+    coeff2 = convert_vector_basis(coeff, np.eye(5), overlap_cp)
+    desired = np.array([-0.5 - 0.5 * 4.0 + 6.0, 3.0, 5.0,
+                        0.86602540378 * 1.0 - 0.86602540378 * 4.0, 2.0])
+    assert_allclose(coeff2, desired)
+
+
+def test_converting_from_pure_to_cartesian():
+    # Test converting S-type.
+    overlap_cp = tfs[0]
+    coeff = np.array([5.])
+    coeff2 = convert_vector_basis(coeff, np.eye(1), overlap_cp.T)
+    assert_equal(coeff, coeff2)
+
+    # Test converting P-type.
+    overlap_cp = tfs[1]
+    coeff = np.array([1., 2., 3.])
+    coeff2 = convert_vector_basis(coeff, np.eye(3), overlap_cp.T)
+    desired = np.array([2., 3., 1.])
+    assert_equal(coeff2, desired)
+
+    # Test converting D-type.
+    overlap_cp = tfs[2]
+    coeff = np.array([1., 2., 3., 4., 5.])
+    coeff2 = convert_vector_basis(coeff, np.eye(6), overlap_cp.T)
+    desired = np.array([np.sqrt(3.0) * 4.0 / 2.0 - 0.5, 5.0, 2.0,
+                        -np.sqrt(3.0) * 4.0 / 2.0 - 0.5, 3.0, 1.0])
+    assert_equal(coeff2, desired)