Merge branch 'master' into dp/poincare

desc/grid.py

@@ -1648,25 +1648,27 @@ def most_rational(a, b, itol=1e-14):
     """
     a = float(_round(a, itol))
     b = float(_round(b, itol))
-    # handle empty range
+
+    # Handle empty range
     if a == b:
         return a
-    # ensure a < b
-    elif a > b:
-        c = a
-        a = b
-        b = c
-    # return 0 if in range
+
+    # Return 0 if in range
     if np.sign(a * b) <= 0:
         return 0
-    # handle negative ranges
-    elif np.sign(a) < 0:
+
+    # Handle negative ranges
+    if np.sign(a) < 0:
         s = -1
         a *= -1
         b *= -1
     else:
         s = 1
 
+    # Ensure a < b
+    if a > b:
+        a, b = b, a
+
     a_cf = dec_to_cf(a)
     b_cf = dec_to_cf(b)
     idx = 0  # first index of dissimilar digits

tests/test_grid.py

@@ -14,6 +14,7 @@
     dec_to_cf,
     find_least_rational_surfaces,
     find_most_rational_surfaces,
+    most_rational,
 )
 from desc.profiles import PowerSeriesProfile
 
@@ -823,6 +824,33 @@ def test_find_most_rational_surfaces():
     np.testing.assert_allclose(rho, np.linspace(0, 1, 5), atol=1e-14, rtol=0)
     np.testing.assert_allclose(io, np.linspace(1, 3, 5), atol=1e-14, rtol=0)
 
+    # simple test, linear iota going from -1 to -3
+    iota = PowerSeriesProfile([-1, -2])
+    rho, io = find_most_rational_surfaces(iota, 5)
+    np.testing.assert_allclose(rho, np.linspace(0, 1, 5), atol=1e-14, rtol=0)
+    np.testing.assert_allclose(io, np.linspace(-1, -3, 5), atol=1e-14, rtol=0)
+
+    # invalid (a > b) ranges and negative ranges are swapped and made positive
+    all_same = [
+        most_rational(1, 2),
+        most_rational(2, 1),
+        most_rational(-1, -2),
+        most_rational(-2, -1),
+    ]
+
+    assert len(set(map(abs, all_same))) == 1
+
+    # if 0 in range, return 0
+    has_zero = [
+        most_rational(0, 1),
+        most_rational(0, -1),
+        most_rational(0, 0),
+        most_rational(-1, 0),
+        most_rational(1, 0),
+    ]
+
+    assert all(result == 0 for result in has_zero)
+
 
 @pytest.mark.unit
 def test_find_least_rational_surfaces():