[gecode-users] int vs. unsigned int for Matrix dimensions

[Christian Schulte]

Hi Gregory,

That looks fine. But there is slightly more to it:
 1) In Gecode we separate declarations from their definitions and use both
inline and 
    forceinline (meaning: must be inlined) to mark them. You might have seen
that.
 2) We would also require documentation in doxygen format (It would be great
if you put
    Everything into a group with a \name annotation, see Gecode for
examples).
 3) It should be done for all arrays: Var, Arg, and View.
 4) You need to be okay with putting stuff under Gecode's license
 5) It would be great if you could give me some examples so that I can add
some doc to MPG.

Thanks!
Christian

--
Christian Schulte, web.ict.kth.se/~cschulte/



-----Original Message-----
From: users-bounces at gecode.org [mailto:users-bounces at gecode.org] On Behalf
Of Gregory Crosswhite
Sent: Thursday, January 20, 2011 7:48 PM
To: users at gecode.org
Subject: Re: [gecode-users] int vs. unsigned int for Matrix dimensions

So, is this design is acceptable to you all, and if so do you want me to 
submit a patch?

Cheers,
Greg

On 01/19/2011 10:54 AM, Gregory Crosswhite wrote:
> Actually, I just came up with a simpler idea:  rather than creating a 
> new iterator class, you could simply use a pointer as the iterator 
> type, so that adding a full set of begin()/end() methods is easy:
>
> #include <iterator> // STL iterator classes
>
> template<class Var> VarArray {
> protected:
>     int n;
>     Var* v;
> public:
>     Var* VarArray::begin() { return v; }
>     Var* VarArray::end() { return v+n; }
>     const Var* VarArray::begin() const { return v; }
>     const Var* VarArray::end() const { return v+n; }
>
>     Var* VarArray::rbegin() { return std::reverse_iterator(end()); }
>     Var* VarArray::rend() { return std::reverse_iterator(begin()); }
>     const Var* VarArray::rbegin() const { return 
> std::reverse_iterator(end()); }
>     const Var* VarArray::rend() const { return 
> std::reverse_iterator(begin()); }
> ...
> };
>
> (And of course the same can be done for ArgArrayBase.)
>
> Adding these methods should be sufficient to allow library users to 
> iterate over your arrays using the standard idioms.
>
> Cheers,
> Greg
>
> On 1/17/11 5:47 AM, Christian Schulte wrote:
>> Hi,
>>
>> Yes, this list is a good forum...
>>
>> Again you caught us red-handed... I know that begin() and end() is the
>> standard idiom but some of our iterators do not naturally fit in this
>> concept (that iterators that iterate over values and ranges of 
>> variables and
>> views).
>>
>> I think what one could do is providing a wrapper class that translates a
>> Gecode-style iterator (using a constructor or init function for
>> initialization, operator ++() for moving to the next element, and 
>> operator
>> ()() for testing whether the operator is done). If you can come up with
>> something like that we would of course integrate it.
>>
>> Best
>> Christian
>>
>> -- 
>> Christian Schulte, www.ict.kth.se/~cschulte/
>>
>>
>> -----Original Message-----
>> From: Gregory Crosswhite [mailto:gcross at phys.washington.edu]
>> Sent: Monday, January 17, 2011 12:36 AM
>> To: users at gecode.org; cschulte at kth.se
>> Subject: Re: [gecode-users] int vs. unsigned int for Matrix dimensions
>>
>> Part of the reason I am asking how to talk to the developers,
>> by-the-way, is because I was thinking it might be useful for the
>> arrays/argument arrays to have an iterator interface added to them, to
>> make it easier to do things like applying generics algorithms to them
>> and traversing them using the c++0x "for each" statement as well as
>> BOOST_FOREACH.  Would there be any interest in a contribution to Gecode
>> to provide this?  The supporting code that I had in mind would include
>> new classes for the iterators and new methods .begin() and .end() for
>> the arrays.
>>
>> Cheers,
>> Greg
>>
>> On 1/16/11 1:46 PM, Gregory Crosswhite wrote:
>>> Okidoke;  thanks for the explanation!  :-)
>>>
>>> Also, is this list the best way to talk to the developers of Gecode?
>>>
>>> Thanks,
>>> Greg
>>>
>>> On 1/16/11 1:10 PM, Christian Schulte wrote:
>>>> Hi Gregory,
>>>>
>>>> You are touching a slightly weird aspect of Gecode... The choice of
>>>> int as
>>>> opposed to unsigned int for the Matrix class is actually deliberate.
>>>> This
>>>> choice is not only done for Matrix but for many other datastructures
>>>> that
>>>> are defined by Gecode (for example, VarArray, ViewArray, etc). I know
>>>> that
>>>> the choice of unsigned int sounds more appealing but we have made the
>>>> opposite decision and try to be as consistent with the choice of int
>>>> rather
>>>> than unsigned int.
>>>>
>>>> There are two reasons. The first is simple and maybe is not even very
>>>> convincing. The average loop written to iterate over arrays etc is
>>>> typically
>>>> an int and not an unsigned int. To avoid compiler warnings, Gecode
>>>> follows
>>>> in this. Then, the second reason (possibly not more convincing than 
>>>> the
>>>> first one) is that integer variables take int values and very often
>>>> array
>>>> access is wrt a value included in the domain of an integer variable.
>>>> Here we
>>>> go.
>>>>
>>>> We tried to use unsigned int but it was in fact just too painful
>>>> (lots of
>>>> explicit casts in order to avoid warnings). Changing int to unsigned
>>>> int and
>>>> be consistent about that change would be a massive effort with little
>>>> gain.
>>>>
>>>> I know. Sad but true.
>>>>
>>>> Cheers
>>>> Christian
>>>>
>>>> -- 
>>>> Christian Schulte, web.ict.kth.se/~cschulte/
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: users-bounces at gecode.org [mailto:users-bounces at gecode.org] On
>>>> Behalf
>>>> Of Gregory Crosswhite
>>>> Sent: Friday, January 14, 2011 6:26 PM
>>>> To: users at gecode.org
>>>> Subject: [gecode-users] int vs. unsigned int for Matrix dimensions
>>>>
>>>> Hey everyone,
>>>>
>>>> Is there a reason why the Matrix class uses "int" for the type of its
>>>> dimensions instead of "unsigned int"?  If there isn't a reason not to
>>>> use "unsigned int" for the type of the dimensions, then may I submit a
>>>> patch or something to change it to use "unsigned int"?
>>>>
>>>> Thanks!
>>>> Greg
>>>>
>>>> _______________________________________________
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>>>>
>>>
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>
>
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