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Runtime Stack Overflow in Recursive Functions

zmleitao

I have implemented a recursive function to explore a circuit hierarchically at the schematic level.

However, for large circuits, such as top-level blocks, I get the following error:

*Error* myRecursiveFunc: Runtime Stack Overflow!!!

 

Is there any way to increase the stack size or the only workaround is to make a non-recursive implementation of the function?

  • Andrew Beckett

    Normally the stack limits in SKILL are big enough that you should never hit these limits for recursing a design hierarchy. Sure, if you're writing a heavily recursive function, it might run out of stack. Also if you have lots of arguments to your recursive function, that eats into the stack space. I just wrote a simple function with 9 arguments and still could cope with over 1600 deep recursive calls... which ought to be enough for a hierarchical design!

    Usually these errors occur because you've made a mistake in the code and the recursion is running away. 

    There's no way to increase the stack size. However, if the recursive function is suitable, you can take advantage of tail call optimization. The function has to be written in "ils" mode (e.g. in a file with a .ils suffix), and you need to turn on:

    sstatus(optimizeTailCall t)

    Also, you may find that even writing the code in SKILL++ mode (ils mode) buys you a bit more stack space too (does in my simple examples).

    Regards,

    Andrew.

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