[tools] adds util function to find 0 vecs in arrays

src/pymor/tools/floatcmp.py

@@ -64,3 +64,24 @@ def bounded(lower, upper, x, rtol=None, atol=None):
         absolute tolerance for float_cmp
     """
     return (lower < x < upper) or float_cmp(x, lower, rtol, atol) or float_cmp(x, upper, rtol, atol)
+
+
+def contains_zero_vector(vector_array, rtol=None, atol=None):
+    """returns `True` iff any vector in the array float_compares to 0s of the same dim
+
+    Parameters
+    ----------
+    vector_array
+        a |VectorArray| implementation
+    rtol
+        relative tolerance for float_cmp
+    atol
+        absolute tolerance for float_cmp
+    """
+    zero = np.zeros(vector_array.dim)
+
+    for i in range(len(vector_array)):
+        vec = vector_array[i].to_numpy()
+        if float_cmp_all(vec, zero, rtol, atol):
+            return True
+    return False