fix bug for reverse unit test.

All tests in local passed

jobs/src/integrators.py

@@ -22,6 +22,7 @@ def verlet(F: Callable, q0: np.ndarray, p0: np.ndarray, m: np.ndarray, dt: float
     return p, q
 
 
+
 def leapfrog(F: Callable, q0: np.ndarray, p0: np.ndarray, m: np.ndarray, dt: float):
     '''
         # using leapfrog integration. https://en.wikipedia.org/wiki/Leapfrog_integration
@@ -36,13 +37,13 @@ def leapfrog(F: Callable, q0: np.ndarray, p0: np.ndarray, m: np.ndarray, dt: flo
     q = q0
 
     # 1. Update Momentum at Half Step:
-    p += dt / 2 * F(q)
+    p = p + dt / 2 * F(q)
 
     # 2. Update Position:
-    q += p / m * dt
+    q = q + p / m * dt
 
     # 3. Update Momentum at Full Step:
-    p += dt / 2 * F(q)
+    p = p + dt / 2 * F(q)
 
     # print("-------------------")
     # print(f'accelerations={accelerations}')
@@ -63,10 +64,10 @@ def stormer_verlet(F: Callable, q0: np.ndarray, p0: np.ndarray, m: np.ndarray, d
 
     # 1. Update Position at Half Step:
     acc = F(q) / m
-    q += p / m * dt + acc * (dt ** 2 * 0.5)
+    q = q + p / m * dt + acc * (dt ** 2 * 0.5)
 
     # 2. Update Momentum:
-    p += acc * (dt * 0.5) * m + F(q) * (dt * 0.5)
+    p = p + acc * (dt * 0.5) * m + F(q) * (dt * 0.5)
 
     return p, q