🚀 go-pugleaf

Bruce Varley <bv@nospam.com> wrote:
> This is an outcome of an industrial problem that's been solved with some 
> brute force computer work, this posting is just a result of my curiosity.
> We had the task of checking an array of integers for duplicates, due to the 
> hardware involved the traditional approaches weren't suitable. One of our 
> people came up with an algo that works for the cases that we encounter in 
> the field,  I'm wondering whether the result holds for all n.
> There is an array of n integers between 1 and n, with no repeated members, 
> in any order. Let P be the product of all the entries, and S be the sum.
> The postulate is that no other set of n integers, all between 1 and n 
> (obviously containing repeats) will have the same values for both P and S.


1 54 55 	sum 110 product 2970

5 6 99

---
You whackos [i.e. "scientists"] just keep changing your "predictions" to suit reality!
  -- BONZO@27-32-240-172 [86 nyms and counting], 16 Feb 2011 15:57 +1100

<kym@kymhorsell.com> wrote in message 
news:4dd7cb2e$0$24911$afc38c87@news.optusnet.com.au...
> Bruce Varley <bv@nospam.com> wrote:
>> This is an outcome of an industrial problem that's been solved with some
>> brute force computer work, this posting is just a result of my curiosity.
>> We had the task of checking an array of integers for duplicates, due to 
>> the
>> hardware involved the traditional approaches weren't suitable. One of our
>> people came up with an algo that works for the cases that we encounter in
>> the field,  I'm wondering whether the result holds for all n.
>> There is an array of n integers between 1 and n, with no repeated 
>> members,
>> in any order. Let P be the product of all the entries, and S be the sum.
>> The postulate is that no other set of n integers, all between 1 and n
>> (obviously containing repeats) will have the same values for both P and 
>> S.
>
>
> 1 54 55 sum 110 product 2970
>
> 5 6 99
>
> ---
> You whackos [i.e. "scientists"] just keep changing your "predictions" to 
> suit reality!
>  -- BONZO@27-32-240-172 [86 nyms and counting], 16 Feb 2011 15:57 +1100

Yep, the conjecture breaks for n=9 also. 

Bruce Varley <bv@nospam.com> wrote:
[...]

What you may be looking for is a "perfect hashing" scheme.
While Don Knuth wrote in his book such schemes might be very dificult
to find, quite a few are now known.

Give it a Google.

There is also a UNIX/Linux/GNU tool called "gperf" that creates perfect
hash tables for strings (normally used for reserved word or keyword lookup)
that might either do what you want or be adapted.

-- 
"Denialism"? Is that a word? 
  -- Mickey Langan, Sun 2 Jan 2011 4:50 pm

<kym@kymhorsell.com> wrote in message 
news:4dd8e833$0$22474$afc38c87@news.optusnet.com.au...
> Bruce Varley <bv@nospam.com> wrote:
> [...]
>
> What you may be looking for is a "perfect hashing" scheme.
> While Don Knuth wrote in his book such schemes might be very dificult
> to find, quite a few are now known.
>
> Give it a Google.
>
> There is also a UNIX/Linux/GNU tool called "gperf" that creates perfect
> hash tables for strings (normally used for reserved word or keyword 
> lookup)
> that might either do what you want or be adapted.
>
> -- 
> "Denialism"? Is that a word?
>  -- Mickey Langan, Sun 2 Jan 2011 4:50 pm

Thanks, I'll follow that up. This function has to run on a specialised 
industrial platform with minimal capabilities (yes, amazingly they do still 
exist), classical algos such as hashing are likely to be OTT. I have a 
couple of workarounds up my sleeve. Cheers 

Bruce Varley <bv@nospam.com> wrote:
...
> Thanks, I'll follow that up. This function has to run on a specialised 
> industrial platform with minimal capabilities (yes, amazingly they do still 
> exist), classical algos such as hashing are likely to be OTT. I have a 
> couple of workarounds up my sleeve. Cheers 

Generalisations of Pearson hashing only require XOR and indexing
into a table.

---
Why have you posted binaries to a text-only newsgroup, fuck wit?
Would you like to see how it appears in a compliant newsreader, which
all of the usenet with IQs beyond single digits use? It appears as
above in the quoted text - NO IMAGES AT ALL! ROTFL
[Seems like "fuckwit" has never seen HTML before].
-- Gillard Lies <oyrooloutacarbontax@gmail.com>, 18 Feb 2011 22:57 -0800 (PST)