[gecode-users] Integer Variable Randomization
Jean-Noël Monette
jean-noel.monette at it.uu.se
Wed Apr 23 18:32:10 CEST 2014
Hi,
Here is my understanding of your problem. If you have N variables, you
will need N decisions to reach a "solution". And at each decision,
Gecode will copy the whole model, that is N variables (Christian,
correct if I am wrong). So the time spent should be at least quadratic
in the number of variables. I am not sure whether the numbers you gave
correspond much more to an exponential increase rather than to a
quadratic increase. So this could be the explanation of your problem. I
think that one way to check this would be to completely disable copying
and replace it by recomputation. I am not sure how this is accomplished
though.
Cheers,
Jean-Noël
On 23/04/14 17:58, negate273 at gmail.com wrote:
> The statistics reveal that the “Peak depth” and “Nodes” are the same as the number of variables. Where can I get the number of “Search steps” ?
> My model did not have *any* constraints (model is copied below).I modified the bounds of the variables to see if the bounds made a difference in the solution time, but it did not.
> MODEL -
> class Money : public Script {
> protected:
> /// Number of letters
> static const int nl = 70000; // <---- This number corresponds with NVars listed above.
> /// Array of letters
> IntVarArray le;
> public:
> /// Model variants
> enum {
> MODEL_SINGLE, ///< Use single linear equation
> MODEL_CARRY ///< Use carries
> };
> /// Actual model
> Money(const Options& opt) : le(*this,nl,0,65535) { // <----------BOUNDS for integer variable
> Rnd rnd(314) ;
> branch(*this, le, INT_VAR_SIZE_MIN(), INT_VAL_RND(rnd)); // <-------Random numbers to integers.
> }
> /// Print solution
> virtual void
> print(std::ostream& os) const {
> // os << "\t" << le << std::endl;
> }
>
> /// Constructor for cloning \a s
> Money(bool share, Money& s) : Script(share,s) {
> le.update(*this, share, s.le);
> }
> /// Copy during cloning
> virtual Space*
> copy(bool share) {
> return new Money(share,*this);
> }
> };
>
> /** \brief Main-function
> * \relates Money
> */
> int
> main(int argc, char* argv[]) {
> Options opt("SEND+?MORE=MONEY");
> opt.model(Money::MODEL_SINGLE);
> opt.solutions(1);
> Script::run<Money,DFS,Options>(opt);
> std::cout << "--- \n" ;
> return 0;
> }
> On Apr 21, 2014, at 4:12 AM, Christian Schulte <cschulte at kth.se> wrote:
>
>> Just check the number of search steps needed, it can tell you something more
>> important than time.
>>
>> Then (I am guessing here), given that your model is based on money it has
>> lost of linear constraints in it, right? There you will only get propagation
>> if by branching either the lower or upper bound of the values for a variable
>> changes. If you just randomize you are likely to choose an inner value which
>> might not give that much propagation.
>>
>> Best
>> Christian
>>
>> --
>> Christian Schulte, KTH, web.it.kth.se/~cschulte/
>>
>> -----Original Message-----
>> From: users-bounces at gecode.org [mailto:users-bounces at gecode.org] On Behalf
>> Of negate273 at gmail.com
>> Sent: Monday, April 21, 2014 02:47 AM
>> To: users at gecode.org
>> Subject: [gecode-users] Integer Variable Randomization
>>
>> Hi, I'm seeing an exponential time increase in the time to just randomize
>> integer variables. My test program is based on "examples/money.cpp" , and I
>> removed the constraints and simply randomize the integer variables by using
>> INT_VAL_RND()
>> -> branch(*this, le, INT_VAR_SIZE_MIN(), INT_VAL_RND(rnd));
>> Is the exponential increase in time with the number of integer random
>> variables in Gecode expected ? and if so, why. And can this be improved by
>> modifying the model ?
>> Thanks..
>>
>> NVars SolveTime(in Seconds)
>> 10000 0.734
>> 20000 3.267
>> 30000 7.67
>> 40000 18.262
>> 50000 31.274
>> 60000 50.674
>> 70000 73.82
>>
>> Complete Test program -
>>
>> #include <gecode/driver.hh>
>> #include <gecode/int.hh>
>> #include <gecode/minimodel.hh>
>>
>> using namespace Gecode;
>>
>> class Money : public Script {
>> protected:
>> /// Number of letters
>> static const int nl = 70000; // <---- This number corresponds with
>> NVars listed above.
>> /// Array of letters
>> IntVarArray le;
>> public:
>> /// Model variants
>> enum {
>> MODEL_SINGLE, ///< Use single linear equation
>> MODEL_CARRY ///< Use carries
>> };
>> /// Actual model
>> Money(const Options& opt) : le(*this,nl,0,65535) { // <----------
>> BOUNDS for integer variable
>> Rnd rnd(314) ;
>> branch(*this, le, INT_VAR_SIZE_MIN(), INT_VAL_RND(rnd)); // <-------
>> Random numbers to integers.
>> }
>> /// Print solution
>> virtual void
>> print(std::ostream& os) const {
>> // os << "\t" << le << std::endl;
>> }
>>
>> /// Constructor for cloning \a s
>> Money(bool share, Money& s) : Script(share,s) {
>> le.update(*this, share, s.le);
>> }
>> /// Copy during cloning
>> virtual Space*
>> copy(bool share) {
>> return new Money(share,*this);
>> }
>> };
>>
>> /** \brief Main-function
>> * \relates Money
>> */
>> int
>> main(int argc, char* argv[]) {
>> Options opt("SEND+?MORE=MONEY");
>> opt.model(Money::MODEL_SINGLE);
>> opt.solutions(1);
>> Script::run<Money,DFS,Options>(opt);
>> std::cout << "--- \n" ;
>> return 0;
>> }
>>
>> // STATISTICS: example-any
>>
>>
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>
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