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Re: FindInstance does not abort with TimeConstrained

  • To: mathgroup at smc.vnet.net
  • Subject: [mg115455] Re: FindInstance does not abort with TimeConstrained
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Tue, 11 Jan 2011 19:20:48 -0500 (EST)

eqnA = Rationalize[
    -0.41593500000000005*(1 - t)*(1 - u)*(1 - v) -
     0.5155109999999999*t*(1 - u)*(1 - v) -
     0.415706*(1 - t)*u*(1 - v) -
     0.5152300000000001*t*u*(1 - v) +
     0.20544400000000002*(1 - t)*(1 - u)*v +
     0.30929599999999996*t*(1 - u)*v +
     0.20519199999999999*(1 - t)*u*v +
     0.30898500000000007*t*u*v, 0] // Simplify;

eqnB = Rationalize[
    -0.08238600000000001*(1 - t)*(1 - u)*(1 - v) +
     0.11608500000000001*t*(1 - u)*(1 - v) -
     0.082311*(1 - t)*u*(1 - v) +
     0.116053*t*u*(1 - v) +
     0.15861400000000003*(1 - t)*(1 - u)*v +
     0.5001389999999999*t*(1 - u)*v +
     0.15848999999999996*(1 - t)*u*v +
     0.49979000000000007*t*u*v, 0] // Simplify;

eqnC = Rationalize[
    0.12412599999999999*(1 - t)*(1 - u)*(1 - v) +
     0.160255*t*(1 - u)*(1 - v) +
     0.043126*(1 - t)*u*(1 - v) +
     0.097819*t*u*(1 - v) +
     0.404011*(1 - t)*(1 - u)*v +
     0.5547869999999999*t*(1 - u)*v +
     0.308304*(1 - t)*u*v +
     0.47778400000000004*t*u*v, 0] // Simplify;

Reduce[{eqnA == 0, eqnB == 0, eqnC == 0,
  0 <= t <= 1, 0 <= u <= 1, 0 <= v <= 1},
 {t, u, v}, Reals]

False

Relaxing the constraints

Reduce[{eqnA == 0, eqnB == 0, eqnC == 0,
   0 <= t, 0 <= u, 0 <= v},
  {t, u, v}, Reals, Backsubstitution -> True] // N

(t == 4.40375 && u == 1914.31 && v == 0.0657319) || (t == 5.3339 && 
   u == 1442.6 && v == 1.36694)


Bob Hanlon

---- leongz <leongz86 at gmail.com> wrote: 

=============
I am trying to find a solution to a set of three equations in three
variables using FindInstance. Since I would like the computation to
abort when it is taking too long, I wrapped it in TimeConstrained.
However, the computation fails to abort, and even pressing Alt-. does
not help. Appreciate any help. Thanks.

My code is as follows, on Mathematica 8.

eqnA = -0.41593500000000005*(1 - t)*(1 - u)*(1 - v) -
  0.5155109999999999*t*(1 - u)*(1 - v) - 0.415706*(1 - t)*u*(1 - v) -
  0.5152300000000001*t*u*(1 - v) +
  0.20544400000000002*(1 - t)*(1 - u)*v +
  0.30929599999999996*t*(1 - u)*v + 0.20519199999999999*(1 - t)*u*v +
  0.30898500000000007*t*u*v
eqnB = -0.08238600000000001*(1 - t)*(1 - u)*(1 - v) +
  0.11608500000000001*t*(1 - u)*(1 - v) -
  0.082311*(1 - t)*u*(1 - v) + 0.116053*t*u*(1 - v) +
  0.15861400000000003*(1 - t)*(1 - u)*v +
  0.5001389999999999*t*(1 - u)*v + 0.15848999999999996*(1 - t)*u*v +
  0.49979000000000007*t*u*v
eqnC = 0.12412599999999999*(1 - t)*(1 - u)*(1 - v) +
  0.160255*t*(1 - u)*(1 - v) + 0.043126*(1 - t)*u*(1 - v) +
  0.097819*t*u*(1 - v) + 0.404011*(1 - t)*(1 - u)*v +
  0.5547869999999999*t*(1 - u)*v + 0.308304*(1 - t)*u*v +
  0.47778400000000004*t*u*v

eqnA = Chop[FullSimplify[eqnA], 0.0001]
eqnB = Chop[FullSimplify[eqnB], 0.0001]
eqnC = Chop[FullSimplify[eqnC], 0.0001]

TimeConstrained[
 FindInstance[{eqnA == 0, eqnB == 0, eqnC == 0, 0 <= t <= 1,
   0 <= u <= 1, 0 <= v <= 1}, {t, u, v}, Reals]
 , 1]



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