[gecode-users] Possible Bug - Increase IntVars Range and Gecode Stalls

[Navid Mohaghegh]

Hi Everyone,

My question:
I am wondering what is happening in below and why Gecode stalls stall whenI increase the range of my IntegerVars (while its CPU utilization goes very high) despite the fact that our constraints are not changed?

Background (http://navid.ca/gecode/test.cpp):
We are trying to solve a space. We can easily solve the space when our variable ranges are small (e.g. 0 to 800). As soon as the range goes higher (e.g. 0-1535) Gecode will stall and can not produce a solution for the space with exactly the same constraints as before.

We have 4 groups of integer_array variables. They are called vars_a, vars_b, vars_c and vars_d. And inside each of them, we have 15 integer variables.
NavidTest(int n, int vars_a_max_, int vars_b_max_, int vars_c_max_, int vars_d_max_, int vcost_max_); 
NavidTest* m = new NavidTest(15,  800, 500, 410, 60, 2000000000); means:
n = 15
vars_a[0] ... vars_a[15] can have values from zero to vars_a_max_ = 800
vars_b[0] ... vars_b[15] can have values from zero to vars_b_max_ = 500
vars_c[0] ... vars_c[15] can have values from zero to vars_c_max_ = 410
vars_d[0] ... vars_d[15] can have values from zero to vars_d_max_ = 60
our cost variable can be have values from zero to vcost_max_ = 2,000,000,000
As we have quadratic cost functions and values can easily grow.
lift() method is where we add our constraints. 
For demonstration purpose, we have a method that once used, Gecode can produce solution: it is called "void the_one_works()"
And we have another one (called: void the_one_doesnot_work) that can not be solved using Gecode (it is perfectly solvable and we test our solution in verify_answer() method)
The only difference between the_one_works() and the_one_doesnot_work() is an increase in vars_a max range from 800 to 1535. 



I have found a mailing list entry stating a possible bug:
==========
From: victor.zverovich at ... <victor.zverovich at ...>
Subject: bug in INT_VALUES_MAX
Newsgroups: gmane.comp.lib.gecode.user
Date: 2013-06-21 22:20:18 GMT (29 weeks, 3 days, 17 hours and 17 minutes ago)
There seems to be a trivial bug in INT_VALUES_MAX: SEL_VALUES_MIN is used instead of SEL_VALUES_MAX. The attached patch fixes it.
Victor
==========

Can someone have a look and let me know?
We are using Gecode 4.2.1 on Linux
GCC 4.7.2 and also latest 4.9
Debian 64bit and CentOS 64bit  
My code and how I compile and run is here: http://navid.ca/gecode/test.cpp

Thank you,
Navid

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