Questions tagged [findinstance]
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38
questions
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Why does `FindInstance` refuse to find a second instance, in a number theory problem?
Hi I am looking for reversible Markov generating matrices of order three, whose upper (2,2) block has integer eigenvalues. There are 5 free parameters; I specified 2
...
2
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1answer
55 views
Does FindInstance traverse the entire domain?
If the result of FindInstance[expr<=0,vars,dom] is empty set, can it mean that expr is always greater than ...
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1answer
59 views
How to show all global minimizers?
This is a follow-up to this question and I'm aware of this question for the local minimizers case.
Consider, for $0\leq \epsilon\leq 1$ and $0<q,p<1$, the function
$$
\begin{align}
f(\...
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0answers
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Finding multiple minimizers
Is it possible to find all (or as many as possible) minimizers of a given function? For example, minimizing the function $\cos(\pi(p-q))+\cos(\pi(q+p))$ for $-3\leq p,q\leq 3 $ can be done using ...
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4answers
267 views
FindInstance won't compute this simple expression
I want to find instances where this standard 3x3 symmetric matrix has only positive eigenvalues.
So I run ...
1
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1answer
32 views
Find a non-convex instance for a non-convex set function with FindInstance
Let $f$ be a non-convex set function defined on a set $L$.
Hence there are subsets $A,B\subseteq L$ such that
$$f(A)+f(B)>f(A\cup B)+f(A\cap B).$$
I tried to use FindInstance function to find a non-...
1
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1answer
58 views
Obtain fairly sampled data set subject to a condition?
I need to obtain a random distribution of some parameters {t1,t2,t3} subject to a set of conditions. For example,
...
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0answers
58 views
FindInstance taking too long
I just started to use Wolfram Alpha Notebook Edition. I am using FindInstance command to evaluate the sign of an expression with $8$ variables, under simple constraints, but it takes too much time. Do ...
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48 views
Why does specifying the solution domain seriously affect the solution speed?
I want to solve the problem of this post. After trying, I found a strange problem.
When I specify the solution field as a real field, the code runs all the time:
...
asked Aug 13 '20 at 0:35
A little mouse on the pampas
5,1602 gold badges9 silver badges28 bronze badges
0
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2answers
142 views
My Program using NSolve and FindInstance has been running for days without a solution
I have a system of 5 non-linear equations and 5 unknowns (p1,p2,p3,p4,p5 bellow), and a few inequalities. I am trying to understand whether the solution is unique.
For this purpose, I tried to run ...
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119 views
System of 15 equations in 23 variables
$$
1-k_0^2=0, \frac{1}{2} \left(-7 \alpha ^2+38 \alpha +2 c_3 (\alpha +\beta-3)+2 c_6-2 k_1^2-2 k_5^2-48\right)=0, c_5-k_2^2-k_{10}^2=0, c_8(\alpha +\beta -5)+5 c_{10}-k_3^2-k_6^2-k_8^2-k_{11}^2-2 k_2 ...
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1answer
82 views
Solve inequalities
I use FindInstance to find a set of real parameters to satisfy the following inequality
$-3 c_{11}-k_4^2-k_7^2-k_9^2>0$,
$$
-4 \alpha^6+84 \alpha^5-721 \alpha^4+3228 \alpha^3-7924 \alpha^2+10080 \...
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1answer
84 views
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2answers
47 views
How can I find some values for which an expression is real?
I've a complicated expression which depends on several variables. I want to find some values for those variables such that the complicated expression is real. How can I do that?
The obvious command ...
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54 views
Turning FindInstance into True or False
I have a function where I input a certain vector of parameters and it gives me the output of 16 FindInstances. So, a typical output will look something like this
...
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0answers
53 views
Finding a solution to a modular problem efficiently
I want to find a naïve hash function of the form Mod[a x + b, 2^p] which would produce a value less or equal to v for all ...
3
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1answer
121 views
Why does FindInstance take so long: It is faster with more restrictions than with less?
A support case with the identification [CASE:4347836] was created.
I just noted this little puzzle on twitter by Brillant.org:
\begin{align} A B C\\+ BCA\\ = CDE \end{align}
Given that $A$ is even ...
1
vote
1answer
43 views
FindInstance confused by CoprimeQ
For some reason when I type
FindInstance[a + b == c && CoprimeQ[a, b, c] == True, {a, b, c}, Integers]
Mathematica just immediately returns my input as ...
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1answer
61 views
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0answers
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FindInstance Returns “Aborted” [closed]
Edit: Apologies, the question needs to be reworked, because I cannot reproduce the original problem using this code.
I don't delete the question, in case someone is preparing an answer at the moment.
...
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2answers
51 views
How to use a given list of values for a parameter in FindInstance?
How should I specify a discrete range for a parameter as one of the conditions in FindInstance? MemberQ/Element functions don't seem to work.
For example,
...
3
votes
1answer
87 views
FindInstance and cosine system of equations
I'm intrigued by Mathematica indisposition to find an example of the following system of equations
$$
\cos(x) + \cos(y) + \cos(z) = \lambda_1,
$$
$$
\cos(x+u) + \...
6
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1answer
92 views
What are the 'special or interesting points in the set' returned by FindInstance?
The documentation for FindInstance[] says:
The instances returned by FindInstance typically correspond to special or ...
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65 views
Why is FindInstance unable to find multiple pythagorean triples?
If I input the code
FindInstance[x^2 + y^2 == z^2 && 0 < x && 0 < y && 0 < z, {x, y, z}, Integers, 2]
Mathematica outputs
"...
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1answer
80 views
Reducing system of 10 inequalities
I have the following system of inequalities of real variables
...
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2answers
137 views
Improving FindInstance efficiency
I am relatively new to Mathematica and my function has been running for over a month now. I am beginning to think I may never get a solution or that there is a mistake in the code, which means a ...
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2answers
128 views
On the solvability of the Diophantine equation $a(x^2-y^2)+2bxy=1$
Take two integers $a,b$ with $\mathrm{GCD}(a,b)=1$ and $a$ odd. Consider the Diophantine equation
$$
a(x^2-y^2)+2bxy=1,\qquad x,y\in\mathbb Z
$$
Is there any efficient way to determine whether such ...
asked Nov 14 '18 at 17:45
AccidentalFourierTransform
9,1021 gold badge15 silver badges48 bronze badges
0
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1answer
311 views
FindInstance with a symbolic constant
Please consider
FindInstance[m >= 0 && x >= 0 && x <= m, {x}]
for which, I would like a parametric answer ...
2
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1answer
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FindInstance within a range
I am trying to find particular solutions to my inequality for two positive integers $a$ and $b$:
FindInstance[a<f[etc...]*b,{a,b},Integers]
However I want $a$ ...
1
vote
3answers
122 views
Checking Rationality Using FindInstance
I need to find example if $x,\sqrt{x^2+6},\sqrt{x^2+12}$ all can be rational at once or not. But the following command
...
3
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4answers
360 views
Problems with FindInstance in v. 11
I have been trying to solve a system of linear equations and linear inequalities with 18 unknowns. I would think that for Mathematica giving an answer to such question will be a matter of milliseconds....
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0answers
521 views
solving linear systems with parameters
I am trying to solve simple, small linear systems, with parameters. I would like to have the result shown for various values of the parameter. RowReduce[],
...
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What is the algorithm used in FindInstance? [closed]
Is FindInstance guaranteed to find an instance if one exists? Conversely, if it does not find an instance, does that mean an instance does not exist at all? Finally, is there a way to change the ...
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361 views
Faster way to pick pairs of integer coordinates from a “region”
I am trying to find a faster way to do this than what I have put together or by looping through a bunch of points.
I want to select all pairs of integer points ((x1,y1),(x2,y2)) such that:
Point (x1,...
0
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1answer
129 views
Get a feasible solution
Link : Reduce time taken to get feasible solution
I have 18 inequations with 4 variables vars2 = {arb[1], arb[2], arb[3], arb[4]} , To get a feasible solution, NMinimize and Nmaximize were used as ...
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Error using NMinimize/NMaximize : The initial region specified may not contain any feasible points
Link : Reduce time taken to get feasible solution
An example of 18 non linear inequations with 4 variables is given in the image. But I have a set of 32 non linear inequations with 9 variables (I ...
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(FindInstance) Speeding up a slow integer program by converting to a boolean program
Here is an integer program with a bunch of inequality and equality constraints. FindInstance takes 2 seconds to solve it.
...
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FindInstance boolean program is slow, but fast with BooleanConvert
FindInstance can be incredibly slow to solve a boolean program, but it can be significantly improved by using BooleanConvert to ...
