Re: [boost] Rounding, Truncating Values

From: Paul A Bristow (pbristow_at_[hidden])
Date: 2008-06-04 12:04:37

Perhaps we can suggest it for GSoC next year?  I'll try to remember to do that - but your supervision/mentoring will be invaluable.

I vaguely recall that an unlimited precision integer would be needed? Or was it just a big/whopper integer? This would be valuable
as a Boost thingy anyway?

Paul

---
Paul A Bristow
Prizet Farmhouse, Kendal, Cumbria UK LA8 8AB
[phone] & SMS, Mobile [phone] & SMS
pbristow_at_[hidden]
 
>-----Original Message-----
>From: boost-bounces_at_[hidden] 
>[mailto:boost-bounces_at_[hidden]] On Behalf Of Hervé Brönnimann
>Sent: 04 June 2008 06:12
>To: boost_at_[hidden]
>Subject: Re: [boost] Rounding, Truncating Values
>
>Paul:  Most valuable indeed.  Like a bullion of gold, because in  
>practice they aren't much slower than the run-of-the-mill sscanf/ 
>sprintf (a few extra cycles, except once in a while in spurious  
>boundary cases where you need more than one or two extra binary  
>digits).  But the guaranteed round-trip, and extra precision, is well  
>worth it.  But who's got the time... <insert here great  
>proselytization about boost, library code, reuse, etc.> :)
>
>Oh, I remember fondly implementing Bellerophon in grad school  
>(Clinger's original scanf).  We had two weeks in Dave Hanson's  
>systems programming class, 40% of the grade for the code working on  
>the given examples, 40% for working on his test suite -- which he  
>*didn't* give us access to, and 20% for the style/doc.  In 13 weeks,  
>we worked 13 problems (two weeks each, one week to research/read and  
>discuss during the next class, overlapping with implementing the  
>previous project).  Projects ranged from various SIGPLAN/research  
>recent or classical articles illustrating systems issues, e.g. this  
>(floating point), impl. a context switcher for Solaris threads in  
>assembler, impl. a symbolic tree manip for optimization (Dave gave us  
>his lcc compiler, we only tweaked the optimizing module), some new/ 
>improved graph algorithm for manipulating symbols in a linker's  
>symbol table, a couple of hard optimization problems (with  
>heuristics), incl. some speach audio data analysis, etc.  You get the  
>idea.
>
>Dave's class was the best programming class I ever took, and one I  
>hope to teach again myself someday.  If any teacher/instructor is  
>listening, this is a formula I most highly recommend.  Keeps everyone  
>honest, and teaches discipline like nothing else.  (Lots of work for  
>the teacher though; Dave had set up a black-box server wherein we  
>could test our program, and output had to be *identical*, a la ACM  
>Competition; grading was automatic by running private test suite and  
>diff'ing the outputs.)
>
>I got Bellerophon to work all right, it isn't that hard if you follow  
>the math (not a small feat, though), but it requires meticulous  
>implementation skills (and will beat it into you if you don't have  
>it).  Then begins the fun with infinities and nans...  and for  
>dessert: subnormal numbers.
>
>Either one (both?) would be a great SoC project, by the way, if any  
>student is listening, once you have the right interface.
>--
>Hervé Brönnimann
>hervebronnimann_at_[hidden]
>
>
>On Jun 3, 2008, at 10:59 AM, Paul A Bristow wrote:
>
>>
>> I've glanced at the Burger and Dybvig algorithms you quote, but  
>> they don't seem too simple to implement.  If any one can get they to
>> work, they would be most valuable.