Enhance statistics

handel/interface.py

@@ -38,6 +38,28 @@ Stats = namedtuple(
     'Stats', 'realtime livetime triggers events icr ocr deadtime')
 
 
+def stats_from_buffer(array):
+    # Raw statistics
+    realtime = float(array[0])
+    livetime = float(array[1])
+    triggers = int(array[3])
+    events = int(array[4])
+
+    # ICR/OCR computation
+    # It turns out the hardware only keeps the integer part of the rate
+    # computations. It is improved here.
+    icr = triggers / livetime
+    ocr = events / realtime
+    assert int(icr) == int(array[5])
+    assert int(ocr) == int(array[6])
+
+    # Deadtime computation
+    # It's unclear whether icr=ocr=0 should result in a 0.0 or 1.0 deadtime
+    deadtime = 1 - float(ocr) / icr if icr != 0 else 1.
+
+    return Stats(realtime, livetime, triggers, events, icr, ocr, deadtime)
+
+
 def to_bytes(arg):
     if isinstance(arg, bytes):
         return arg
@@ -174,19 +196,9 @@ def get_module_statistics(module):
     code = handel.xiaGetRunData(master, b'module_statistics', data)
     check_error(code)
     # Parse raw data
-    result = {}
-    for index, channel in enumerate(channels):
-        if channel != -1:
-            realtime = array[index * 7 + 0]
-            livetime = array[index * 7 + 1]
-            triggers = int(array[index * 7 + 3])
-            events = int(array[index * 7 + 4])
-            icr = int(array[index * 7 + 5])
-            ocr = int(array[index * 7 + 6])
-            deadtime = 1 - float(ocr) / icr if icr != 0 else 1.
-            result[channel] = Stats(
-                realtime, livetime, triggers, events, icr, ocr, deadtime)
-    return result
+    return {channel: stats_from_buffer(array[index * 7:])
+            for index, channel in enumerate(channels)
+            if channel != -1}
 
 
 def get_statistics():

tests/test_interface.py

@@ -277,13 +277,28 @@ def test_get_module_statistics(interface):
     m = interface.handel.xiaGetRunData
 
     def side_effect(channel, dtype, arg):
-        arg[3*7:4*7] = [1.0, 2.0, 255, 3, 4, 8, 6]
+        arg[3*7:4*7] = [
+            1.00758784,
+            0.98603936,
+            255.,
+            3088.,
+            2742.,
+            3131.,
+            2721.]
         return 0
 
+    expected = {8: interface.Stats(
+        1.00758784,
+        0.98603936,
+        3088.,
+        2742.,
+        3131.720827046904,
+        2721.350825353351,
+        0.13103658479051494)}
+
     m.side_effect = side_effect
     with mock.patch('handel.interface.get_module_channels') as m2:
         m2.return_value = [-1, -1, -1, 8]
-        expected = {8: interface.Stats(1.0, 2.0, 3, 4, 8, 6, 0.25)}
         assert interface.get_module_statistics('module3') == expected
         m2.assert_called_once_with('module3')
         arg = m.call_args[0][2]