PPL for linear expression comparison and constraint derivation
Dear Sir/Madam, I am interested in starting to use Parma Polyhedra library for my research. I do have a specific problem and I would like to check whether PPL could be used for solving. I need to compare two linear expression and derive the necessary constraints on the variables such that one of them is minimum/maximum. For example, what should be the relation between x, a and b such that 3x+a+5b is smaller than x+5a+3b (just an example I haven’t paid attention to the actually numbers). Are there functions in PPL that I could use to solve this? Thank you in advance for your time, Aleksandra Jovanovic Aleksandra Jovanovic Research Assistant Department of Computer Science University of Oxford Wolfson Building, Parks Road Oxford, OX1 3QD
On 09/19/14 18:56, Aleksandra Jovanovic wrote:
I am interested in starting to use Parma Polyhedra library for my research. I do have a specific problem and I would like to check whether PPL could be used for solving.
I need to compare two linear expression and derive the necessary constraints on the variables such that one of them is minimum/maximum. For example, what should be the relation between x, a and b such that 3x+a+5b is smaller than x+5a+3b (just an example I haven’t paid attention to the actually numbers). Are there functions in PPL that I could use to solve this?
Dear Alexandra, does the following answer your question? $ cat p.cc #include <ppl.hh> using namespace std; using namespace Parma_Polyhedra_Library; using namespace Parma_Polyhedra_Library::IO_Operators; int main() { NNC_Polyhedron ph(3); Variable A(0); Variable B(1); Variable C(2); ph.add_constraint(3*A + B + 5*C < A + 5*B + 3*C); cout << ph.minimized_constraints() << endl; return 0; } $ g++ -W -Wall p.cc -lppl -lgmpxx -lgmp $ a.out -A + 2*B - C > 0 $ Note that I interpreted "smaller" as "strictly smaller". If strict constraints are not required, using C_Polyhedron instead of NNC_Polyhedron will be more efficient. Please do not hesitate to come back to us (by writing to ppl-devel@cs.unipr.it) if I misinterpreted your question or you need more information. Kind regards, Roberto -- Prof. Roberto Bagnara Applied Formal Methods Laboratory - University of Parma, Italy mailto:bagnara@cs.unipr.it BUGSENG srl - http://bugseng.com mailto:roberto.bagnara@bugseng.com
Dear Professor, Thank you very much, this indeed seems to be exactly what I needed. I am sorry for the late reply I am attending a conference at the moment. Thank you once again, Aleksandra Jovanovic Aleksandra Jovanovic Research Assistant Department of Computer Science University of Oxford Wolfson Building, Parks Road Oxford, OX1 3QD On 19 Sep 2014, at 19:13, Roberto Bagnara <bagnara@cs.unipr.it> wrote:
#include <ppl.hh>
using namespace std; using namespace Parma_Polyhedra_Library; using namespace Parma_Polyhedra_Library::IO_Operators;
int main() { NNC_Polyhedron ph(3); Variable A(0); Variable B(1); Variable C(2); ph.add_constraint(3*A + B + 5*C < A + 5*B + 3*C); cout << ph.minimized_constraints() << endl; return 0; }
participants (2)
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Aleksandra Jovanovic -
Roberto Bagnara