Talk:Pi

Why "until a key is pressed"? That's an annoyingly non-portable construct. --Rdm 22:20, 25 March 2011 (UTC)

I wrote the break key. Someone else wrote "until a key is pressed". The idea is that the process runs for infinity unless the process is terminated. I have reverted the wording to say "the break key".

Markhobley 22:40, 25 March 2011 (UTC)

Using a keyboard is non-portable? The break key is less portable. I changed it to any key to try to make it more general. Really it should just go forever if you want it to be portable. In general, portability is not necessarily a concern here I don't think. --Mwn3d 02:15, 26 March 2011 (UTC)

I agree. There are computers without a keyboard, and special industrial keyboards with the break key removed. If there is no facility to terminate the process, then it should run for infinity for the purposes of this task. I have updated the wording to clarify this point.

Markhobley 10:57, 26 March 2011 (UTC)

I take it that you are looking for until the process is terminated, in whatever way is normal for the environment, not necessarily with a key labeled “Break”. I have updated the task description to clarify this. —Kevin Reid 13:35, 27 March 2011 (UTC)

Why request "continue for infinity"? There are no computer that has infinity memory so that request will simply not be possible. A practical limit "continue as long as possible" could make more sense. --<Jofur> 11:02, 26 March 2011 (UTC)

Indeed. Infinity here means until the limits of the computer are reached. (So on a system that uses 32 bit registers, calculations would probably cease after 4294967295 digits, unless big numbering was used.)

Markhobley 15:54, 26 March 2011 (UTC)

There are basiclly two ways to calculate Pi that I know of; #1, (traditional) to calculate the sequence in a row & #2 (BBP-Formual) that calculates specific digits in base-16... Both needs huge amount of memory and if you aim for 'infinity' the #1 system will likely crash due to the data arrays and #2 due to the huge polynoms used for the smallest fractions - neither will give anything close to 4294967295 digits on a 32-bit system.

If to behave nice, maybe the program should end before it crash? --<Jofur> 16:28, 26 March 2011 (UTC)

How?

The task should provide at least one method for doing such a calculation I think? --Paddy3118 17:10, 26 March 2011 (UTC)

I left this open for the coder to decide at this stage, but I would probably use bbp to obtain each consecutive digit. (We could always split the task for different methodologies in future).

Markhobley 21:21, 26 March 2011 (UTC)

It can still be left up to the programmer, but maybe offer some suggestions with pseudocode? People don't have to generate infinite digits of pi very often. They probably don't have algorithms lying around in their brains. --Mwn3d 21:25, 26 March 2011 (UTC)

There's an algorithm that allows you to calculate a specific digit of pi. I'd google it, but I'm about to head out the door. It might be possible to memoize some of the intermediate values. --Michael Mol 13:36, 27 March 2011 (UTC)

bbp? --Paddy3118 22:46, 26 March 2011 (UTC)

Deleted GUISS solution

GUISS uses the desktop calculator for this task, and produces the maximum number of digits that the desktop calculator produces. ("Forever" in computing terms means until the maximum value of the registers is reached, or resources are exhausted, rather than "forever" as in the life of the Universe). The GUISS solution provided the closest approximate fit based on its capabilities. Maybe I should have stuck a note that the solution provided produces as many digits as possible for the implementation. (It is not possible to get more digits). The solution was deleted, but I will restore it and pin a note. Markhobley 22:34, 23 July 2011 (UTC)

So "my language can only quote windows calcualator, and windows calculator can only provide 16 digits" is your defense? Assuming that's what you meant by "resources", then your language is incapable of meeting reasonable human expectations of this task, and the decent thing to do is just say so. Why would you rather find some loophole and try to squeeze a "solution" in here, what's the point of that? --Ledrug 00:13, 24 July 2011 (UTC)

So that we can compare the approaches in different langauges. This is a chrestomathy. The only options are to provide a best fit solution or omit, unless you have some other ideas. What do you suggest? Markhobley 01:13, 24 July 2011 (UTC)

I think as long we provide suitable comments explaining that the solution does not meet the task exactly, and give the reasoning, then that should be fine. Markhobley 01:16, 24 July 2011 (UTC)

Give some example wording here if you like, and I will paste it into the description. The reason is as you say: The calculator only provides 16 digits. Markhobley 01:18, 24 July 2011 (UTC)

Every solution on the page will come to a limit, because of the nature of the task. With GUISS, the limit is 16 digits, other solutions may stop after a few thousand digits, but they will stop.Markhobley 01:27, 24 July 2011 (UTC)

I'm not sure using the windows calculator really fits the task because (as far as I know) it doesn't actually calculate anything--it spits out a stored value. Otherwise I could say "System.out.println(Math.PI);" for Java and call it a day. That feels like cheating. --Mwn3d 04:50, 24 July 2011 (UTC)

I don't know Java. Could you set the precision to a high number of digits, and then System.out.println(Math.PI)? I think a two line solution would be cool. Markhobley 11:23, 24 July 2011 (UTC)

Presumably not, because it would be limited to the precision of the conventional floating point, like most other languages, or does it support arbitrary precision? Markhobley 11:27, 24 July 2011 (UTC)

In no way does the GUISS solution fit the spirit of the task and should be removed. In what way does it give successive digits of Pi, "until aborted by the user"? The task description is clearly asking that you use a routine that generates the digits of Pi in sequence - GUISS does not ensure that and so should be removed. The GUISS example does not aid language comparison - it stands out as an anomaly. --Paddy3118 05:37, 24 July 2011 (UTC)

Hmmm, It does generate the digits o Pi in sequence. There is an abort button on the calculator, but I don't know whether it works midflow. By replacing the desktop calculator with one that uses a bigger display to get more digits and supports abortion midflow. The GUISS solution would fit the task. The limitation is with the tool provided, rather than with GUISS. Markhobley 09:11, 24 July 2011 (UTC)

Maybe a "limited solution" marker would be a good idea. (Similar to the "incorrect solution", that reads something like 'The solution provided does not meet the exact specifications of the task, due to limitations of the language or its subcomponents. The author has tried to provide an "approximate fit" solution based on those limitations'.). I know there are other tasks on the wiki, where the solutions are an approximation, rather than an exact fit. This might be quite useful. Markhobley 09:45, 24 July 2011 (UTC)

This is not strictly true. The underlying concept -- that each solution has finite limits -- is true. However, it's not the case that we can say that all solutions would their limit if they were allowed to run indefinitely. A solution could have an time increase between each digit, ensuring that the solution does not terminate before reaching a finite limit (let's say a billion digits before the heat death of the universe) because each successive digit takes so much longer than the previous digit. --Rdm 10:52, 24 July 2011 (UTC)