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Entry  05 Sep 2024, Jack Carlton, Forum, Python frontend rate limitations? frontend.pyfrontend.cxx
    Reply  05 Sep 2024, Ben Smith, Forum, Python frontend rate limitations? 
       Reply  05 Sep 2024, Stefan Ritt, Forum, Python frontend rate limitations? 
          Reply  06 Sep 2024, Jack Carlton, Forum, Python frontend rate limitations? 
          Reply  11 Sep 2024, Konstantin Olchanski, Forum, Python frontend rate limitations? 
    Reply  11 Sep 2024, Konstantin Olchanski, Forum, Python frontend rate limitations? 
       Reply  11 Sep 2024, Konstantin Olchanski, Forum, Python frontend rate limitations? 
Message ID: 2825     Entry time: 05 Sep 2024     Reply to this: 2826   2831
Author: Jack Carlton 
Topic: Forum 
Subject: Python frontend rate limitations? 
I'm trying to get a sense of the rate limitations of a python frontend. I 
understand this will vary from system to system.

I adapted two frontends from the example templates, one in C++ and one in python. 
Both simply fill a midas bank with a fixed length array of zeros at a given polled 
rate. However, the C++ frontend is about 100 times faster in both data and event 
rates. This seems slow, even for an interpreted language like python. Furthermore, 
I can effectively increase the maximum rate by concurrently running a second 
python frontend (this is not the case for the C++ frontend). In short, there is 
some limitation with using python here unrelated to hardware.

In my case, poll_func appears to be called at 100Hz at best. What limits the rate 
that poll_func is called in a python frontend? Is there a more appropriate 
solution for increasing the python frontend data/event rate than simply launching 
more frontends?

I've attached my C++ and python frontend files for reference.

Thanks,
Jack
Attachment 1: frontend.py  4 kB  Uploaded 05 Sep 2024  | Hide | Hide all | Show all
import midas
import midas.frontend
import midas.event
import numpy as np
import random
import time

class DataSimulatorEquipment(midas.frontend.EquipmentBase):
    def __init__(self, client, frontend):
        equip_name = "Python Data Simulator"
        default_common = midas.frontend.InitialEquipmentCommon()
        default_common.equip_type = midas.EQ_POLLED
        default_common.buffer_name = "SYSTEM"
        default_common.trigger_mask = 0
        default_common.event_id = 2
        default_common.period_ms = 100
        default_common.read_when = midas.RO_RUNNING
        default_common.log_history = 1
        
        midas.frontend.EquipmentBase.__init__(self, client, equip_name, default_common)
        print("Initialization complete")
        self.set_status("Initialized")

        self.frontend = frontend

    def readout_func(self):
        event = midas.event.Event()
        
        # Create a bank for zero buffer
        event.create_bank("CR00", midas.TID_SHORT, self.frontend.zero_buffer)
        
        # Simulate the addition of `data` in the periodic event
        '''
        data_block = []
        data_block.extend(self.frontend.data)
        
        
        # Append the simulated data to the event
        event.create_bank("CR00", midas.TID_SHORT, data_block)
        '''

        return event
    
    def poll_func(self):
        current_time = time.time()
        if current_time - self.frontend.last_poll_time >= self.frontend.poll_time:
            self.frontend.last_poll_time = current_time
            self.frontend.poll_count += 1
            self.frontend.poll_timestamps.append(current_time)
            return True  # Indicate that an event is available
        return False  # No event available yet

class DataSimulatorFrontend(midas.frontend.FrontendBase):
    def __init__(self):
        midas.frontend.FrontendBase.__init__(self, "DataSimulator-Python")
        
        # Data and zero buffer initialization
        self.data = []
        self.zero_buffer = []
        self.generator = random.Random()
        self.total_data_size = 1250000
        self.load_data_from_file("fake_data.txt")
        self.init_zero_buffer()

        # Polling variables
        self.poll_time = 0.001  # Poll time in seconds
        self.last_poll_time = time.time()
        self.poll_count = 0
        self.poll_timestamps = []

        self.add_equipment(DataSimulatorEquipment(self.client, self))

    def load_data_from_file(self, filename):
        try:
            with open(filename, 'r') as file:
                for line in file:
                    values = [int(value) for value in line.strip().split(',')]
                    self.data.extend(values)
            print(f"Loaded data from {filename}: {self.data[:10]}...")  # Display the first few values for verification
        except IOError as e:
            print(f"Error opening file: {e}")

    def init_zero_buffer(self):
        self.zero_buffer = [0] * self.total_data_size 
        print(f"Initialized zero buffer with {self.total_data_size } zeros.")

    def begin_of_run(self, run_number):
        self.set_all_equipment_status("Running", "greenLight")
        self.client.msg(f"Frontend has started run number {run_number}")
        return midas.status_codes["SUCCESS"]

    def end_of_run(self, run_number):
        self.set_all_equipment_status("Finished", "greenLight")
        self.client.msg(f"Frontend has ended run number {run_number}")
        
        # Print poll function statistics at the end of the run
        self.print_poll_stats()

        return midas.status_codes["SUCCESS"]

    def frontend_exit(self):
        print("Frontend is exiting.")

    def print_poll_stats(self):
        if len(self.poll_timestamps) > 1:
            intervals = [self.poll_timestamps[i] - self.poll_timestamps[i-1] for i in range(1, len(self.poll_timestamps))]
            avg_interval = sum(intervals) / len(intervals)
            print(f"Poll function was called {self.poll_count} times.")
            print(f"Average interval between poll calls: {avg_interval:.6f} seconds")
        else:
            print(f"Poll function was called {self.poll_count} times. Not enough data for interval calculation.")

if __name__ == "__main__":
    with DataSimulatorFrontend() as my_fe:
        my_fe.run()
Attachment 2: frontend.cxx  7 kB  Uploaded 05 Sep 2024  | Show | Hide all | Show all
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