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idata
Community Manager
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Problems with Python Multiprocessing using SDK 2.0.0.4

Using device on a Rpi 3 Model B+ with the latest OS for a robotics project

 

I'm using SSD MobileNets to do real time object detection for the robot. I kickoff a process to do the predictions function (similar def run_inference function in the Movidius NC App Zoo GitHub example (https://github.com/movidius/ncappzoo/blob/master/caffe/SSD_MobileNet/run.py)). The function works fine when its part of the main but it won't execute when dispatch it another core. I believe the issue is it can find the device. I'm surmising this because I tried to open the device on a core other then the main and got the following error:

 

W: [ 0] ncDeviceOpen:505 ncDeviceOpen() XLinkBootRemote returned error 3

 

the TraceBack toot me here:

 

File "/usr/local/lib/python2.7/dist-packages/mvnc/mvncapi.py", line 448, in open

 

raise Exception(Status(status))

 

Exception: Status.ERROR

 

Can the Movidius device only work on the main core on Rpi? Any help would be greatly appreciated.

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6 Replies
idata
Community Manager
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@sggriset Check to see if your process running on the main core if it has released the device handle for the NCS device. It seems like the device may still be pegged on the main core.

idata
Community Manager
207 Views

Sorry for the long response. I turned off the Rpi 3 and unplugged the NCS device. I booted the Rpi3 and ran lsusb both without and with the NCS plugged in to get the VID & PID and got the following read out:

 

pi@edge_rover:~ $ cd ~/edge_rover/edge_runner pi@edge_rover:~/edge_rover/edge_runner $ lsusb Bus 001 Device 004: ID 0424:7800 Standard Microsystems Corp. Bus 001 Device 003: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub Bus 001 Device 002: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub pi@edge_rover:~/edge_rover/edge_runner $ lsusb Bus 001 Device 005: ID 03e7:2150 Bus 001 Device 004: ID 0424:7800 Standard Microsystems Corp. Bus 001 Device 003: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub Bus 001 Device 002: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub pi@edge_rover:~/edge_rover/edge_runner

 

So the VID = 0x3e7 and PID = 0x2150 are these for the NCS device. Then put this python snippet based on the program the hello_ncs.py snippet

 

# import necessary libs import multiprocessing as mp import usb.core import usb.util import mvnc.mvncapi as movi VID = 0x03e7 PID = 0x2150 def find_dev(): mob_device = usb.core.find(idVendor=VID, idProduct=PID) if not mob_device: print "[INFO] Movidius Device Not Found" exit(1) print "[INFO] Found Movidius Device" # set the logging level for the Movidius device movi.global_set_option(movi.GlobalOption.RW_LOG_LEVEL, 0) devices = movi.enumerate_devices() if(len(devices) < 1): print("[INFO] Error - no Movidius devices detected") exit(1) # get the first NCS device dev = movi.Device(devices[0]) try: dev.open() except: print("[INFO] Error - Could not open NCS device.") exit(1) print("[INFO] NCS Device is found") try: dev.close() except: print("[INFO] Error - could not close device") exit(1) print("[INFO] NCS Device closed normally") print("NCS device working,") exit(0) def main(): devtest = mp.Process(target = find_dev) devtest.start() pid = devtest.pid print(pid) devtest.join() if __name__ == '__main__': main()

 

I ran the program and got the following results

 

[INFO] Found Movidius Device D : [ 0] ncDeviceCreate:307 ncDeviceCreate index 0 D : [ 0] ncDeviceCreate:307 ncDeviceCreate index 1 D : [ 0] ncDeviceOpen:501 File path /usr/local/lib/mvnc/MvNCAPI-ma2450.mvcmd I: [ 0] ncDeviceOpen:507 ncDeviceOpen() XLinkBootRemote returned success 0 W: [ 0] ncDeviceOpen:533 failed to find device [INFO] Error - Could not open NCS device.

 

Now when I run lsusb

 

Bus 001 Device 006: ID 03e7:f63b Bus 001 Device 004: ID 0424:7800 Standard Microsystems Corp. Bus 001 Device 003: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub Bus 001 Device 002: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

 

So it looks like when you try to open the device in core other then in the main core it changes the PID (product ID). Can you please run a test using my snippet, I think I may have a bad device.

idata
Community Manager
207 Views

Sorry something happen with the paste on the code snippet:

 

# import necessary libs import multiprocessing as mp import usb.core import usb.util import mvnc.mvncapi as movi VID = 0x03e7 PID = 0x2150 def find_dev(): mob_device = usb.core.find(idVendor=VID, idProduct=PID) if not mob_device: print "[INFO] Movidius Device Not Found" exit(1) print "[INFO] Found Movidius Device" # set the logging level for the Movidius device movi.global_set_option(movi.GlobalOption.RW_LOG_LEVEL, 0) devices = movi.enumerate_devices() if(len(devices) < 1): print("[INFO] Error - no Movidius devices detected") exit(1) # get the first NCS device dev = movi.Device(devices[0]) try: dev.open() except: print("[INFO] Error - Could not open NCS device.") exit(1) print("[INFO] NCS Device is found") try: dev.close() except: print("[INFO] Error - could not close device") exit(1) print("[INFO] NCS Device closed normally") print("NCS device working,") exit(0) def main(): devtest = mp.Process(target = find_dev) devtest.start() pid = devtest.pid print(pid) devtest.join() if __name__ == '__main__': main()
idata
Community Manager
207 Views

@sggriset You said the NCS device works normally, but you were having issues when using multiprocessing? Try using multiprocessing.set_start_method('forkserver'). This will allow the child process to share the environment with the parent. So in main(), change the code to:

 

def main(): mp.set_start_method('forkserver') devtest = mp.Process(target = find_dev) devtest.start() pid = devtest.pid print(pid) devtest.join()

idata
Community Manager
207 Views

Tome_at_intel

 

I apologize for the slow response to your workaround. I tested it and it worked, thank you so much for your support.

idata
Community Manager
207 Views

@sggriset Glad it worked out for you.

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