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Re: FindInstance does not abort with TimeConstrained

  • To: mathgroup at smc.vnet.net
  • Subject: [mg115449] Re: FindInstance does not abort with TimeConstrained
  • From: DrMajorBob <btreat1 at austin.rr.com>
  • Date: Tue, 11 Jan 2011 06:58:36 -0500 (EST)

Deleting all the Simplify and Chop stuff since it doesn't do anything but  
take up time, we can write:

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;

Solve[{eqnA == 0, eqnB == 0, eqnC == 0}, {t, u, v}]

{{t -> -3.19687, u -> 3.28488, v -> -3.31651}, {t -> -2.33029,
   u -> 720.405, v -> -8.27168}, {t -> -0.606671, u -> 1245.81,
   v -> -6.30374}, {t -> -0.280957, u -> 2.95134,
   v -> 0.688093}, {t -> 4.40375, u -> 1914.31,
   v -> 0.0657319}, {t -> 5.3339, u -> 1442.6, v -> 1.36694}}

None of the solutions satisfy your bounds on the variables.

There is also a warning message, but I suspect Solve did what is possible.

You can replace the reals using Rationalize[#,0]&, but Solve found no  
solutions in that case.

Bobby

On Mon, 10 Jan 2011 23:30:54 -0600, 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]
>


-- 
DrMajorBob at yahoo.com


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