Bug introduced in 10.4 and fixed in 10.4.1

I used to have no trouble opening multiple instances of the Mathematica notebook/kernel on Windows by right-clicking on the Mathematica icon in the task bar and then clicking "Wolfram Mathematica 10". Now, after upgrading to 10.4, I instead get the following error message in the currently open Mathematica:

Cannot infer format of file Mathematica.exe.

I get the above message in the Messages window, and I get a new notebook window with a single $Failed entry in it. Never used to get this before.

  • 6
    $\begingroup$ Interesting, I didn't notice this yet, but I can confirm that it's doing the same thing on my (Windows 10) machine. $\endgroup$ Commented Mar 18, 2016 at 13:15
  • 3
    $\begingroup$ I had not tried this yet, but I confirm that I have the same problem on Win7-64. I think you should report this to Wolfram Support. $\endgroup$
    – MarcoB
    Commented Mar 18, 2016 at 14:34
  • $\begingroup$ I do this always in 10.3 and now after this report I am hesitating to upgrade to 10.4 :( $\endgroup$ Commented Mar 18, 2016 at 16:57
  • 2
    $\begingroup$ This bug is already fixed in the development version, unfortunately no workaround is available for 10.4. $\endgroup$
    – ilian
    Commented Mar 18, 2016 at 19:25
  • $\begingroup$ @Algohi: I would always suggest to keep at least one older version installed. I have never had any problems with parallel installations of Mathematica (currently have about 6 installed on my computer)... $\endgroup$ Commented Mar 18, 2016 at 20:34

1 Answer 1



There are easier ways to perform simultaneous evaluations in Mathematica, with notebooks that remain in separate contexts, all within a single instance of the Front End.

First, we will explore how you can access more kernels from your current session, allowing simultaneous evaluation in separate notebooks:

  1. In a notebook, go to Evaluation -> Kernel Configuration Options from the toolbar.
  2. Click Add
  3. Name the secondary kernel, and ensure that "Local Machine" is checked.
  4. Press OK

Now in a notebook, if you go to Evaluation -> Notebook's Kernel -> select your new kernel, it will do its evaluations outside of the local kernel that opens by default. Now, you are able to perform simultaneous evaluations on two notebooks.

You can read more about this here, under Details:


To remove a notebook from the Global` context, you can go to Evaluation -> Notebook's Default Context -> Unique to this Notebook.

Combining these two processes should give you results identical to a notebook that you would have by simultaneously opening two Front Ends -- without the strain on your machine of having two Front Ends running.

While it is not ideal, it is what I am currently able to provide as a workaround to this particular issues in version 10.4.


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