fix: Correctly generates monte carlo version of xy model dipoles

pdme/model/log_spaced_random_choice_xy_model.py

@@ -107,15 +107,14 @@ class LogSpacedRandomCountMultipleDipoleFixedMagnitudeXYModel(DipoleModel):
 			rng = rng_to_use
 
 		shape = (monte_carlo_n, self.n_max)
-		theta = 2 * numpy.pi * rng.random(shape)
-		phi = numpy.arccos(2 * rng.random(shape) - 1)
+		phi = 2 * numpy.pi * rng.random(shape)
 
 		p_mask = rng.binomial(1, self.prob_occupancy, shape)
 		p_magnitude = self.pfixed * p_mask
 
-		px = p_magnitude * numpy.cos(theta) * numpy.sin(phi)
-		py = p_magnitude * numpy.sin(theta) * numpy.sin(phi)
-		pz = p_magnitude * numpy.cos(phi)
+		px = p_magnitude * numpy.cos(phi)
+		py = p_magnitude * numpy.sin(phi)
+		pz = p_magnitude * 0
 
 		sx = rng.uniform(self.xmin, self.xmax, shape)
 		sy = rng.uniform(self.ymin, self.ymax, shape)

tests/model/test_log_spaced_random_count_multiple_dipole_fixed_magnitude_xy_model.py

@@ -97,6 +97,66 @@ def test_random_count_multiple_dipole_fixed_mag_model_get_dipoles_invariant_xy()
 			)
 
 
+def test_random_count_multiple_dipole_fixed_mag_model_get_dipoles_invariant_monte_carlo_xy():
+
+	x_min = -10
+	x_max = 10
+	y_min = -5
+	y_max = 5
+	z_min = 2
+	z_max = 3
+	p_fixed = 10
+	max_frequency = 5
+	monte_carlo_n = 20
+
+	model = LogSpacedRandomCountMultipleDipoleFixedMagnitudeXYModel(
+		x_min, x_max, y_min, y_max, z_min, z_max, 0, max_frequency, p_fixed, 1, 0.5
+	)
+	model.rng = numpy.random.default_rng(1234)
+
+	dipole_arrangement = model.get_dipoles(5)
+	dipoles = dipole_arrangement.dipoles
+
+	assert len(dipoles) == 1, "Should have only had one dipole generated."
+	for i in range(10):
+		dipoles = model.get_monte_carlo_dipole_inputs(monte_carlo_n, max_frequency)
+
+		min_s = numpy.array([x_min, y_min, z_min])
+		max_s = numpy.array([x_max, y_max, z_max])
+
+		_logger.warning(dipoles)
+		_logger.warning(dipoles[:, 0, 0:3])
+		_logger.warning(dipoles[:, 0, 3:6])
+		_logger.warning(dipoles[:, 0, 6])
+
+		ps = dipoles[:, 0, 0:3]
+		ss = dipoles[:, 0, 3:6]
+		ws = dipoles[:, 0, 6]
+
+		numpy.testing.assert_equal(
+			numpy.logical_and(min_s < ss, max_s > ss).all(),
+			True,
+			f"Dipole location [{ss}] should have been between min [{min_s}] and max [{max_s}] bounds.",
+		)
+		assert (ws < 10**max_frequency).all() and (
+			ws > 10**0
+		).all(), "Dipole frequency should have been between 0 and max."
+
+		norms = numpy.linalg.norm(ps, axis=1)
+		filtered_norms = norms[norms > 0]
+		numpy.testing.assert_allclose(
+			filtered_norms,
+			p_fixed,
+			err_msg="Should have had the expected dipole moment magnitude.",
+		)
+
+		numpy.testing.assert_allclose(
+			ps[:, 2],
+			0,
+			err_msg="Should have had zero z magnitude.",
+		)
+
+
 def test_random_count_multiple_dipole_shape():
 
 	x_min = -10