NVIDIA IPython Notebook Based Lab FAQ

Sections

General Questions

Q: How to tell if the server is executing code, or is not working properly.

There are two things to look for to determine if the server is actively executing your code:

  1. At the top-left of the cell block you are executing, you should see In[*] and not In[ ] or In[<some number>].
  2. In addition, and most importantly, you will see a box at the top right of the webpage showing "Kernel Busy".  It will usually look like: 

If you only see #1 and not #2, then you need to refer to the Troubleshooting section.

Q: How to stop a long-running command, such as an infinite loop.

You can try pressing the Stop button on the toolbar at the top of the browser window to stop any activity the Notebook is currently processing.

Q: What is the IPython Notebook infrastructure all about

Try watching this video to get a better understanding of how the IPython Notebook is used in NVIDIA's self-paced labs.

Troubleshooting

Q: Unable to see output returned after executing a cell which is supposed to display something.

There could be a number of reasons for this.

  1. Connecting to an IPython Notebook requires a WebSocket connection and only the following browsers work:

    • Chrome 14 or above
    • Firefox 6 or above
    • Opera 12.10 or above
    • Safari 5 or above
    • Internet Explorer 10

  2. If you are using a supported web browser, and have never gotten output from a Cell block as instructed in each Notebook, it's possible your Antivirus software is blocking WebSockets. The following are methods for avoiding this problem on three popular antivirus software programs.

    NOTE: Please be cautious while browsing other websites after implementing any of these methods. It's also advised to undo them after you are done with this lab.

    Sophos Endpoint Security and Control

    1. From the Windows Start menu, choose Run.
    2. In the dialog box that appears, type services.msc; then click the OK button.
    3. Locate the running Sophos Web Intelligence service, right-click and choose Stop
    4. Reload the IPython Notebook page

    AVG Anti-Virus LinkScanner Surf-Shield

    1. Use the AVG icon in the Windows system tray (notification area) to open the AVG Anti-Virus main window.?
    2. Click LinkScanner.
    3. Disable (uncheck) the Enable Surf-Shield option.
    4. Click the Save changes button.
    5. If you are using Windows 7, click the Yes button at the prompt from User Account Control.

    ESET NOD32 Antivirus

    1. Use the NOD32 icon in the Windows system tray (notification area) to open the NOD32 window.
    2. Press F5.
    3. On the left side of the Advanced Setup window, click the plus signs to expand Web and email and Web access protection; then select URL address management.
    4. In the drop-down list on the right side of the window, select List of addresses excluded from filtering, as shown above.
    5. Enable (check) the List active option, as shown above.
    6. Below the list, click the Add button; type in <endpoint address above>* (be sure to include the asterisk after the “1”).
    7. Click the OK button; then close the NOD32 window.

  3. It's possible your network connection is blocking the use of WebSockets. You can test this by going to websocketstest.com and verify that the "WebSockets (Port 80)" box has 4 green check marks in it.  If this is not the case, please contact your system admin for support.

Q: The Notebook stopped responding after it had been working for awhile

You can try the following to restart the Notebook:

  1. Try saving the Notebook by pressing the Save button on the toolbar near the top of the browser window.
  2. Save any documents you've changed if there are text editors embedded in the Notebook.
  3. Restart the IPython kernel by going to Kernel on the toolbar and selecting Restart. Confirm you want to Restart.
  4. Refresh the whole webpage
    • If you were working on a Python-based lab, you will have to re-execute all previous cells to get the contents back into the active runspace.
    • For non-Python based labs, you do not need to do this.
  5. Try restarting from where you left off.

If the above does not work (or if the Toolbar has frozen), try these steps:

  1. Try saving the Notebook by pressing the Save button on the toolbar near the top of the browser window.
  2. Save any documents you've changed if there are text editors embedded in the Notebook.
  3. Close the Notebook tab.
  4. On the IPython Notebook dashboard where you selected your Notebook, press the "Shutdown" button on the right side of the window.
  5. Click on the Notebook link to restart it.