Merge pull request #97 from robotpy/looptimer

Add LoopTimer object for measuring the performance of robot loops

Author: virtuald

docs/robotpy_ext.misc.rst

@@ -9,6 +9,15 @@ robotpy_ext.misc.asyncio_policy module
     :undoc-members:
     :show-inheritance:
 
+robotpy_ext.misc.looptimer module
+---------------------------------------
+
+.. automodule:: robotpy_ext.misc.looptimer
+    :members:
+    :undoc-members:
+    :show-inheritance:
+
+
 robotpy_ext.misc.precise_delay module
 -------------------------------------
 

robotpy_ext/misc/looptimer.py

@@ -0,0 +1,65 @@
+
+import math
+import wpilib
+
+_getFPGATimestamp = wpilib.Timer.getFPGATimestamp
+
+class LoopTimer:
+    '''
+        A utility class that measures the number of loops that a robot program
+        executes, and computes the min/max/average period for loops in the last
+        second.
+        
+        Example usage::
+        
+            class Robot(wpilib.IterativeRobot):
+        
+                def teleopInit(self):
+                    self.loop_timer = LoopTimer(self.logger)
+                
+                def teleopPeriodic(self):
+                    self.loop_timer.measure()
+        
+        Mainly intended for debugging purposes to measure how much lag.
+    '''
+    
+    def __init__(self, logger):
+        self.logger = logger
+        self.timer = wpilib.Timer()
+        self.timer.start()
+        
+        self.reset()
+        
+    def reset(self):
+        self.timer.reset()
+        
+        self.start = self.last = _getFPGATimestamp()
+        self.min_time = math.inf
+        self.max_time = -1
+        self.loops = 0
+        
+    
+    def measure(self):
+        '''
+            Computes loop performance information and periodically dumps it to
+            the info logger.
+        '''
+        
+        # compute min/max/count
+        now = _getFPGATimestamp()
+        diff = now - self.last
+        self.min_time = min(self.min_time, diff)
+        self.max_time = max(self.max_time, diff)
+        
+        self.loops += 1
+        self.last = now
+        
+        if self.timer.hasPeriodPassed(1):
+            self.logger.info("Loops: %d; min: %.3f; max: %.3f; period: %.3f; avg: %.3f",
+                             self.loops, self.min_time, self.max_time, now - self.start,
+                             (now - self.start) / self.loops)
+            
+            self.min_time = math.inf
+            self.max_time = -1
+            self.start = now
+            self.loops = 0