[racket] universe program using 100% cpu on Mac (also poor Raspberry Pi performance)

TESTS: Say I want to eliminate a common pattern from your handle-key-down function. If it comes with some tests, four to be precise, a simple run -- without playing -- assures me of basic qualities. If you express tests like those below and you formulate them first, you get an idea of how to code the function. And -- for a large function -- a reader quickly gets the idea of how the function works from reading some tests. 

(check-expect (handle-key-down initial-state "w")  (set-left-moving initial-state UP-DIR))

(define (handle-key-down world a-key)
  (cond
    [(key=? a-key "w") (set-left-moving world UP-DIR)]
    [(key=? a-key "s") (set-left-moving world DOWN-DIR)]
    [(key=? a-key "up") (set-right-moving world UP-DIR)]
    [(key=? a-key "down") (set-right-moving world DOWN-DIR)]
    [else world]))

(define (set-left-moving world dir)
  (set-left-paddle world (set-paddle-moving (pong-world-left-paddle world) dir PADDLE-SPEED)))

(define (set-right-moving world dir)
  (set-right-paddle world (set-paddle-moving (pong-world-right-paddle world) dir PADDLE-SPEED)))


GAME PAD: I am happy to see that you used on-pad. Your game does give me an idea on how to improve the whole 'pad situation'. 

-- Matthias





On Dec 29, 2014, at 1:43 PM, Darren Cruse wrote:

> Thanks Matthias and it will be quite fun to tell the others at my next meetup who code reviewed this for me! :)
> 
> I'll make the changes you suggested though (forgive me) I'll have to think about what constitutes useful tests for this.  Somehow I've never fully bought into TDD though I know I'm one of the last holdouts in the civilized world. :)  Can I get out of it saying I was just doing this for fun? :)
> 
> I'm most of all pleased that you didn't see something I'd fundamentally misunderstood, e.g. that would explain why the game performed poorly on the raspberry pi.
> 
> fwiw Racket is the first lispy language I've ever gotten serious about learning.  I'm one of those who'd been thrown off by the parens for too long.  I really like using it now that I'm over the initial learning curve.  I think my biggest wish would be it had a good story for doing smartphone/tablet apps, or that Whalesong was more of a going concern (not that I've tried it I wonder if this pong game would run under it without a ton of work?)
> 
> Thanks again for your time,
> 
> Darren
> 
> 
> On Mon, Dec 29, 2014 at 10:39 AM, Matthias Felleisen <matthias at ccs.neu.edu> wrote:
> 
> Hi Darren, thanks for the link to the repo. I cloned it, successfully played with and without sound on a mac book -- inside of drracket and from the command line-- and never observed a load over 60% for drracket and ditto for plain racket. That doesn't mean that your 100% problem doesn't exist, it's just that I can't reproduce it. 
> 
> A couple of comments on the code: 
> 
>  -- I'd place the main function at the top of the function section of the file 
>       right below the constant definitions and data definitions 
> 	[I modified 2e to bring this across but you might be reading the stable version.]
> 
>  -- I also run (main initial-state) out of the repl not the main buffer. 
> 
>  -- Your file is missing tests. 
> 
>  -- Some functions are also missing proper signatures and purpose statements. 
> 
> But I know "it works" see my homepage :-) 
> 
> -- Matthias
> 
> 
> 
> On Dec 29, 2014, at 10:46 AM, Darren Cruse wrote:
> 
>> Re:
>> Could you post the code somewhere so we can experiment with it? 
>> 
>> Here it is it's all in one file:
>> pong-world.rkt
>> 
>> On Mon, Dec 29, 2014 at 8:05 AM, Matthias Felleisen <matthias at ccs.neu.edu> wrote:
>> 
>> On Dec 28, 2014, at 9:51 PM, Darren Cruse wrote:
>> 
>>> One thing I can see is that on-draw is called for every on-tick on all three platforms btw.
>>> 
>>> And even in cases where the program is idling and on-tick has simply returned the world state it was given unmodified.  
>>> 
>>> Is that normal I wonder?  Part of me thought that since to-draw is a function of the world state, and the world state hasn't changed, that it would *not* call to-draw in that case.
>> 
>> I experimented with this 'optimization' and, if I recall correctly, it didn't make much of a difference and got in the way of imperative world programs. So I took it out. Mea culpa, I should have commented on this experiment inside the code. 
>> 
>> 
>> 
>>> (but it calls to-draw for every on-tick even on the Windows machine which is using only 6% cpu - so maybe I'm wrong to look to that as the problem)
>> 
>> 
>> My Mac-based experiments suggest that this call is not the cause of performance problems. 
>> 
>> ;; --- 
>> 
>> Could you post the code somewhere so we can experiment with it? 
>> 
>> Thanks -- Matthias
>> 
>> 
>> 
> 
> 

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