[erlang-questions] System getting hang after running normal recursion program
Sat Oct 7 14:14:00 CEST 2017
Am aware about tail recursion in erlang, but here I am talking about
recursion which is not tail recursive. Here is the code snippet;
Here the function is not tail recursive and it is in an infinite loop.
If run this function my system is getting hang. That why i got the doubt
why it is making my system to hang and how the erlang scheduler will
behave in this scenario.?
On Saturday 07 October 2017 04:07 PM, Leandro Ostera wrote:
> Hej Arun, hi.
> Depending on your recursion, you may or may not be building up a stack
> that will at some point crash. I am unsure about how C compilers
> typically deal with tail-recursion, but tail call optimization is
> automatically performed in the Erlang VM for you.
> From the Learn You Some Erlang book chapter on Recursion
> *Note:* tail recursion as seen here is not making the memory grow
> because when the virtual machine sees a function calling itself in a
> tail position (the last expression to be evaluated in a function), it
> eliminates the current stack frame. This is called tail-call
> optimisation (TCO) and it is a special case of a more general
> optimisation named /Last Call Optimisation/ (LCO).
> LCO is done whenever the last expression to be evaluated in a function
> body is another function call. When that happens, as with TCO, the
> Erlang VM avoids storing the stack frame. As such tail recursion is
> also possible between multiple functions. As an example, the chain of
> functions |a() -> b(). b() -> c(). c() -> a().| will effectively
> create an infinite loop that won't go out of memory as LCO avoids
> overflowing the stack. This principle, combined with our use of
> accumulators is what makes tail recursion useful.
> Hope this helps!
> On Sat, Oct 7, 2017 at 9:03 AM Arun <arunp@REDACTED
> <mailto:arunp@REDACTED>> wrote:
> Hi all,
> I tried to run normal recursion program from erlang shell, the program
> runs infinitely and it is doing addition of numbers. But its been
> observed that soon after starting the program entire PC is getting
> My doubt is that, why my PC is getting hang. ? , if something is going
> wrong, the erlang vm should be able to handle it, like in C if we run
> some recursion program infinity, it will crash by throwing
> fault error.
> What will be happening in the VM if I run a normal recursion
> program in
> erlang infinitely ?
> What will be the behavior of erlang scheduler in this scenario ?
> Can somebody please assist me on this issue.
> Thanks in advance
> Arun P.
> erlang-questions mailing list
> erlang-questions@REDACTED <mailto:erlang-questions@REDACTED>
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