[PPL-devel] Handling Rational Coefficients

[Tuba Yavuz]

Hello Roberto,

Yes, I was using C++. Section 1.5.10 in the manual made me hope that we 
might be able to input rational coefficients. Now, I understand that we 
need to do some pre-processing to achieve that.

And I found the manual very useful; with the necessary technical 
details.

Thanks for the quick response.

Tuba

On 2016-04-24 11:18, Roberto Bagnara wrote:
> On 24/04/2016 15:14, Tuba Yavuz wrote:
>>
>> Dear PPL Team,
>>
>> I'd like to use PPL for linear arithmetic with rational 
>> coefficients. For instance, I'd like to be able to use constraints 
>> like 0.3*x + 2.66*y >= 1. When I tried to create a NNC_Polyhedra with 
>> that formula, PPL converted it to 2*y >=1.
>>
>> Based on the tutorials, I should be able to use mpq_class to support 
>> rational coefficients. I see that there is an instantiation of 
>> BD_Shape with mp_class specialization. However, I couldn't find 
>> something equivalent for Polyhedra and its subclasses. I also tried to 
>> change the configuration file and set PPL_COEFFICIENT_TYPE to 
>> mpq_class and rebuilt PPL but that didn't seem to work either.
>>
>> I'd appreciate if you could provide me info on this.
>>
>> Regards
>>
>> Tuba
>
> Hello Tuba.
>
> Which interface of the PPL are you using?  C++, I suppose.
> Where did you find in the manual that you could code a constraint
> with C++ code of the form 0.3*x + 2.66*y >= 1 ?
>
> You really need to consult the manual in order to use the PPL.
>
> For the specific thing, if by 0.3 and 2.66 you mean the rational
> numbers with precisely those values, then you can express that
> constraint in the C++ interface, e.g., with 30*x + 266*y >= 100 .
> Kind regards,
>
>    Roberto