Modifies method for swapping edge extremities (#347)

Comparison to find the larger coordinate starts with
checking if these coordinates are close to avoid numerical
problems with float values.

Signed-off by: Ainur Ziganshin
[email protected]

Author: AinurZiga

sionna/rt/solver_base.py

@@ -816,12 +816,22 @@ def _swap_edges(self, edges):
         # 1. norm(p1) >= norm(p0)
         # 2. azimuth(p1) >= azimuth(p0)
         # 3. elevation (p1) >= elevation(p0)
-        needs_swap_1 = r0 > r1
-        not_disc_1 = tf.experimental.numpy.isclose(r0, r1)
-        needs_swap_2 = tf.logical_and(not_disc_1, phi0 > phi1)
-        not_disc_2 = tf.experimental.numpy.isclose(phi0, phi1)
-        not_disc_12 = tf.logical_and(not_disc_1, not_disc_2)
-        needs_swap_3 = tf.logical_and(not_disc_12, theta0 > theta1)
+
+        # More details of the algorithm:
+        # needs_swap 1: !r_equal and r0 > r1
+        # needs_swap 2: r_equal and !phi_equal and phi0 > phi1
+        # needs_swap 3: r_equal and phi_equal and theta0 > theta1
+        # Note: case when all three coordinates are equal is not considered
+
+        r_equal = tf.experimental.numpy.isclose(r0, r1)
+        phi_equal = tf.experimental.numpy.isclose(phi0, phi1)
+        case_2 = tf.logical_and(r_equal, tf.logical_not(phi_equal))
+        case_3 = tf.logical_and(r_equal, phi_equal)
+
+        needs_swap_1 = tf.logical_and(tf.logical_not(r_equal), r0 > r1)
+        needs_swap_2 = tf.logical_and(case_2, phi0 > phi1)
+        needs_swap_3 = tf.logical_and(case_3, theta0 > theta1)
+
         needs_swap = tf.reduce_any(tf.stack([needs_swap_1,
                                              needs_swap_2,
                                              needs_swap_3], axis=1),