Add check for alphas (#21)

Author: prisae

dageo/data_assimilation.py

@@ -13,6 +13,7 @@
 # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 # License for the specific language governing permissions and limitations under
 # the License.
+import warnings
 
 import numpy as np
 
@@ -91,6 +92,10 @@ def esmda(model_prior, forward, data_obs, sigma, alphas=4, data_prior=None,
         alphas = np.zeros(alphas) + alphas
     else:
         alphas = np.asarray(alphas)
+    if abs(np.sum(1/alphas)-1) > 0.01:
+        warnings.warn(
+            f"The sum of 1/alphas should be 1; provided: {np.sum(1/alphas)}."
+        )
 
     # Copy prior as start of post (output)
     model_post = model_prior.copy()

tests/test_data_assimilation.py

@@ -1,3 +1,4 @@
+import pytest
 import numpy as np
 from numpy.testing import assert_allclose
 
@@ -89,6 +90,20 @@ def cbp(x):
     assert_allclose(43420257, np.max(p), atol=1)
     assert_allclose(0.0, x[np.argmax(p)], atol=1e-8)
 
+    # Warning
+    with pytest.warns(UserWarning, match='provided: 1.25'):
+        lm_post3 = dageo.esmda(
+            model_prior=mprior,
+            forward=lin_fwd,
+            data_obs=l_dobs,
+            sigma=obs_std,
+            alphas=[4, 4, 4, 4, 4],
+            localization_matrix=np.array([[0.5]]),
+            callback_post=cbp,
+            return_post_data=False,
+            random=3333,
+        )
+
 
 def test_all_dir():
     assert set(data_assimilation.__all__) == set(dir(data_assimilation))