JohnG

Simple enough problem, but haven't found a solution in the Docs or by googling.

What is the best way to handle exceptions in the perform routine of a MSP external? I'm using some C++ code to do a bit of number crunching, which may throw exceptions. At the moment when this happens Max just crashes, usually taking the whole OS down with it (yes, I'm on windows).

In the create routine you can return 0, which will make your object disabled / unusable. Is there a way to do this from within the perform routine?

Debugging is a right pain if you have to reboot every time an error occurs.

What is the best way to handle exceptions in the perform routine of a MSP external? I'm using some C++ code to do a bit of number crunching, which may throw exceptions. At the moment when this happens Max just crashes, usually taking the whole OS down with it (yes, I'm on windows). 

exception-handling-in-perform-routine

Quote: JohnG wrote on Sun, 13 May 2007 19:39

----------------------------------------------------

> Simple enough problem, but haven't found a solution in the Docs or by googling.

> What is the best way to handle exceptions in the perform routine of a MSP external? I'm using some C++ code to do a bit of number crunching, which may throw exceptions. At the moment when this happens Max just crashes, usually taking the whole OS down with it (yes, I'm on windows). 

> In the create routine you can return 0, which will make your object disabled / unusable. Is there a way to do this from within the perform routine?

> Debugging is a right pain if you have to reboot every time an error occurs.

Quote: JohnG wrote on Sun, 13 May 2007 19:39
----------------------------------------------------
> Hi there,
>
> Simple enough problem, but haven't found a solution in the Docs or by googling.
>
> What is the best way to handle exceptions in the perform routine of a MSP external? I'm using some C++ code to do a bit of number crunching, which may throw exceptions. At the moment when this happens Max just crashes, usually taking the whole OS down with it (yes, I'm on windows). 
>
> In the create routine you can return 0, which will make your object disabled / unusable. Is there a way to do this from within the perform routine?
>
> Debugging is a right pain if you have to reboot every time an error occurs.
>
>
> Thanks,
> John
----------------------------------------------------

Exception handling is typically more expensive than what one wants to 

do within a DSP chain, but the short answer is that if you wish to 

use exception generating code in your perform routine, you have to 

write *your own* exception handling code inside your perform routine. 

As you've surmised, we don't handle perform routine generated C++ 

If you gave more context into what you're trying to do with actual 

code snippets, perhaps someone could offer some suggestions about 

other ways of accomplishing what you're trying to do without 

exceptions. It is something I personally would avoid at all costs 

when trying to perform realtime data processing calculations at high 

sampling rates, though under *very* specific situations, it may not 

> At the moment when this happens Max just crashes, usually taking 

> the whole OS down with it (yes, I'm on windows).

Try using the NRT (non-realtime) audio driver for debugging DSP code. 

This is what it's designed for, despite the fact that some people 

also use it to run CPU exhausting patches. You won't be able hear the 

output, but when it crashes, it shouldn't take down the OS. Also if 

you use Max Runtime, you can attach the debugger and step through 

your code (also recommended only in the NRT audio driver).

> In the create routine you can return 0, which will make your object 

> disabled / unusable. Is there a way to do this from within the 

No. This simply doesn't create an object (rather than an existing, 

but unused object). However, you can decide to not execute whatever 

you want based on a flag of your choosing in the perform routine. So 

again, this responsibility falls on your own implementation of what 

enabled/disabled constitutes, and what mechanism is employed to 

enable/disable your object (e.g. error reached in your DSP code?).

Exception handling is typically more expensive than what one wants to  
do within a DSP chain, but the short answer is that if you wish to  
use exception generating code in your perform routine, you have to  
write *your own* exception handling code inside your perform routine.  
As you've surmised, we don't handle perform routine generated C++  
exceptions in our code.

If you gave more context into what you're trying to do with actual  
code snippets, perhaps someone could offer some suggestions about  
other ways of accomplishing what you're trying to do without  
exceptions. It is something I personally would avoid at all costs  
when trying to perform realtime data processing calculations at high  
sampling rates, though under *very* specific situations, it may not  
be a problem.

>  At the moment when this happens Max just crashes, usually taking  
> the whole OS down with it (yes, I'm on windows).

Try using the NRT (non-realtime) audio driver for debugging DSP code.  
This is what it's designed for, despite the fact that some people  
also use it to run CPU exhausting patches. You won't be able hear the  
output, but when it crashes, it shouldn't take down the OS. Also if  
you use Max Runtime, you can attach the debugger and step through  
your code (also recommended only in the NRT audio driver).

> In the create routine you can return 0, which will make your object  
> disabled / unusable. Is there a way to do this from within the  
> perform routine?

No. This simply doesn't create an object (rather than an existing,  
but unused object). However, you can decide to not execute whatever  
you want based on a flag of your choosing in the perform routine. So  
again, this responsibility falls on your own implementation of what  
enabled/disabled constitutes, and what mechanism is employed to  
enable/disable your object (e.g. error reached in your DSP code?).

I guess I'll just catch the exceptions and use a boolean to enable/disable computation in the perform routine.

I was just wondering if there was a nice way to disable the Max object from within perform, so that by glancing at the patch I can see which object(s) have been disabled (rather than which have simply stopped computation), but I guess not.

I'm not really worried about it from a performance point of view, my CPU usage is still very low. Thanks for the tip about the NRT driver, I'll give it a look.

I guess I'll just catch the exceptions and use a boolean to enable/disable computation in the perform routine. 

Exception Handling In Perform Routine