[Swift-devel] Feedback loops in swift fails with deeper recursion

[Yadu Nand]

Hello Mike,

Sorry about the crude example and even worse explanation.

I'm trying to implement a simple feedback pattern in swift. Here's
what I have : An application foo( ), which feeds back its output till
ome condition cond( ) returns true. cond( ) just checks if a counter
in the file has reached 100. The work( ) app, increments the counter
in the input file by 1. Thus the following pseudo swift code should go
to a 100 level deep recursion.

(file output) foo (file input) {
       if ( input meets conditions ){
             output = input; // tail end of recursion
       } else {
             // do some work on input and pass it back to foo ( )
             file temp = work (input);
             output = foo ( temp );
       }
}

>From what I understand here, the concurrent mapper is creating
temporary files by appending the filename at each level of the
recursion with some chars resulting in filenames exceeding the 255
char limit by the 50th level. I did not know at the time when this
mail was sent out that I could just tell the mapper to name the files
differently.

I could also have used an array of files with the recursion level as
index to retain the file's progress through the recursion and use the
level as an index to previous results.

Thanks,
Yadu

On Wed, Jun 12, 2013 at 11:53 AM, Michael Wilde <wilde at mcs.anl.gov> wrote:
> Yadu, I find your example hard to understand.  Can you clean it up to show what you are really trying to do here?
>
> I dont see where cond changes to terminate the recursion.
>
> Presumably its either for creating a test or for learning the language, but as-it its a bit confusing.
>
> It would also help to show the full script.
>
> If Swift's "concurrent" (default) mapper keeps extending the file name, you should map the files involved explicitly to a name that uses a short integer thats passed as an argument.
>
> - Mike
>
>
> ----- Original Message -----
>> From: "Yadu Nand" <yadudoc1729 at gmail.com>
>> To: "swift-devel" <swift-devel at ci.uchicago.edu>
>> Sent: Wednesday, June 12, 2013 11:35:55 AM
>> Subject: [Swift-devel] Feedback loops in swift fails with deeper recursion
>>
>> The following recursion loop fails at depth >= 50. Swift is
>> generating
>> intermediate files by appending
>> a string to the end of each intermediate file (in my case 5 chars).
>> At
>> depth 50 this exceeds the 255
>> char limit on file names and swift fails with an -1 error code from
>> the user application which could
>> not create the filename swift gave it.
>>
>> (tested on Swift 0.94 swift-r6414)
>>
>> // Recursion loop
>> (file out) reiterate (file input, int cond){
>>       int rval = readData(input);
>>       //tracef("Content passes to reiterate is = %i \n", rval);
>>       if ( check(input, cond) == 1 ){
>>         out = input;
>>         tracef("Reached tail end. Terminating! \n");
>>       }else{
>>         //file temp = process(input);
>>         //out = reiterate(temp, cond);
>>         out = reiterate(process(input), cond);
>>       }
>> }
>>
>> Is there a better way to do feedback of results from the app to
>> itself? Having the app rewrite the input
>> file with the result is IMHO a hack.
>>
>> -Yadu
>> _______________________________________________
>> Swift-devel mailing list
>> Swift-devel at ci.uchicago.edu
>> https://lists.ci.uchicago.edu/cgi-bin/mailman/listinfo/swift-devel
>>



-- 
Yadu Nand B