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Re: Sending an interrupt to the frontend?

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  • Subject: [mg127268] Re: Sending an interrupt to the frontend?
  • From: Ralph Dratman <ralph.dratman at>
  • Date: Thu, 12 Jul 2012 04:58:25 -0400 (EDT)
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In a case like the one you describe, which happens to me two or three
times a day when using Mathematica, I first try the Interrupt command
in the Evaluate Menu. This is by far the best option... if it works --
which is about 40% of the time.

Next comes Quit Kernel, again in the Evaluation menu. Unless the Mac
has run out of free RAM, this almost always works. (To monitor memory
usage, I always keep the Mac's Activity Monitor program open and set
it to display a RAM pie chart, of which the green segment indicates
free memory).  I currently have 8G RAM and plan to upgrade to 16G in
the near future, which in my case means buying a new Mac -- just to
run Mathematica more reliably.

If Quit Kernel fails, I have to force-quit Mathematica, generally from
the Dock. The easiest way to do this is with a right mouse click on
the Mathematica (which incidentally seems odd to me, because most Macs
only have a one-button mouse).

To help prevent this annoying chain of events, I have started using a
little message handler code patch I modified from one I found, either
in this mailing list or at, I am
not sure which.

To use the message handler, put the following at the top of every
source file, or include it as part of a startup file:

(* Interrupt on Message *)
messageHandler = If[Last[#], Interrupt[]] & ;
Internal`AddHandler["Message", messageHandler];

This causes Mathematica to stop whenever it issues any message which
you have not suppressed. I strongly recommend always using this during
testing and debugging. As far as I know, it carries no performance

I hope this helps!

Ralph Dratman

On Tue, Jul 10, 2012 at 3:18 AM, James Stein <mathgroup at> wrote:
> I have experienced the same (or similar) problem.
> For me, it usually occurs unexpectedly, in which case it is likely that I
> have not recently saved the notebook(s) before the evaluation that goes
> awry. After pressing command-period and the menu item "Quit Kernel"
> repeatedly, to no effect, it seems there is no escape except the Macintosh
> "Force Quit" Mathematica, which is always irritating because of the lost
> work and time.
> With years of software experience, I understand why efficient computational
> loops cannot be monitoring a flag or looking for an interrupt; nevertheless
> it would be nice to have a mechanism to stop the kernel without stopping
> the FrontEnd. This would -- I think -- resolve an occasional situtation I
> experience where the Kernel is outputting information faster than the
> FrontEnd can format and display it -- so the FrontEnd seems too busy to
> accept an interrupt and the BackEnd (Kernel) seems unstoppable except via
> the FrontEnd.
> Am I understanding the situation? Perhaps not...
> On Mon, Jul 9, 2012 at 9:40 PM, W Craig Carter <ccarter at> wrote:
>> Hello Mathgroup,
>> This is a question about frozen frontend behavior.
>> In development stages, one of my frequent mistakes is to send the
>> frontend something that takes forever to dynamically update---at least
>> that is what I believe what is happening for most of the "freezing"
>> occurrences.  For MacOs, this is often signaled by a "Formatting
>> Notebook Contents" window.
>> I wonder if anyone has found a method to send the front end a message to
>> stop dynamically updating while in an unresponsive state?  I've various
>> versions of kill -s signal  (i.e., signal = INT) from a terminal in
>> MacOSx, but never with success.
>> I suppose that having the front end query the operating system for
>> interrupt requests would create a lot of overhead.  However, I wonder if
>> a method to force the frontend to make an operating system query with a
>> user-specified time interval might be possible?
>> W Craig Carter

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