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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