I have written an optimization problem in pyomo and need a constraint, which contains a summation that has a variable length:
u_i_t[i, t]*T_min_run - sum (tnewnew in (t-T_min_run+1)..t-1) u_i_t[i,tnewnew] <= sum (tnew in t..(t+T_min_run-1)) u_i_t[i,tnew]
T is my actual timeline and N my machines
usually I iterate over t, but I need to guarantee the machines are turned on for certain amount of time.
def HP_on_rule(model, i, t):
return model.u_i_t[i, t]*T_min_run - sum(model.u_i_t[i, tnewnew] for tnewnew in range((t-T_min_run+1), (t-1))) <= sum(model.u_i_t[i, tnew] for tnew in range(t, (t+T_min_run-1)))
model.HP_on_rule = Constraint(N, rule=HP_on_rule)
I hope you can provide me with the correct formulation in pyomo/python.
The problem is that t is a running variable and I do not know how to implement this in Python. tnew is only a help variable. E.g. t=6 (variable), T_min_run=3 (constant) and u_i_t is binary [00001111100000...] then I get:
1*3 - 1 <= 3
As I said, I do not know how to implement this in my code and the current version is not running.
TypeError: HP_on_rule() missing 1 required positional argument: 't'
It seems like you didn't provide all your arguments to the function rule.
Since t is a parameter of your function, I assume that it corresponds to an element of set T (your timeline).
Then, your last line of your code example should include not only the set N, but also the set T. Try this:
model.HP_on_rule = Constraint(N, T, rule=HP_on_rule)
Please note: Building a Constraint with a "for each" part, you must provide the Pyomo Sets that you want to iterate over at the begining of the call for Constraint construction. As a rule of thumb, your constraint rule function should have 1 more argument than the number of Pyomo Sets specified in the Constraint initilization line.
Related
I'm trying to use the python interface of SCIP tool (https://github.com/scipopt/PySCIPOpt) to solve a mixed-integer optimization problem.
I want to define an OR-constraint with three constraints, but only one of them must be satisfied.
For example, I want to minimize a variable x with three constraints x>=1, x>=2, x>=3, but only one of them must be valid, and then minimize the value of x. Of course the result should be x=1.
However the OR-constraint API addConsOr requires both the constraint list and result variable (resvar, resultant variable of the operation). While I can provide the list of constraints, I don't know the meaning of result variable in the second function parameter. When I set the second parameter to a new variable, the following code cannot run and result in segmentation fault.
from pyscipopt import Model
model = Model()
x = model.addVar(vtype = "I")
b = model.addVar(vtype="B")
model.addConsOr([x>=1, x>=2, x>=3], b)
model.setObjective(x, "minimize")
model.optimize()
print("Optimal value:", model.getObjVal())
Also, setting the second variable to True also gets segmentation fault.
model.addConsOr([x>=1, x>=2, x>=3], True)
What you are describing is not an OR-constraint. An or-constraint is a constraint that takes into account a set of binary variables and gets the result as an OR of these values, as explained in the SCIP documentation.
What you want is a general disjunctive constraint. Those exist in SCIP as SCIPcreateConsDisjunction but are not wrapped in the Python API yet. Fortunately, you can extend the API yourself quite easily. Simply add the correct function to scip.pxd and define the wrapper in scip.pyx. Just look at how it is done for the existing constraint types and do it the same way. The people over at the PySCIPopt GitHub will be happy if you create a pull-request with your changes.
Through trial and error, I have found that the GetPixel function takes two arguments, one for X and one for Y, even if used on a 1D image. On a 1D image, the second index must be set to zero.
image list := [3]: {1,2,3}
list.GetPixel(0,0) // Gets 1
GetPixel(list, 0, 0) // Equivalent
How am I supposed to know this? I can't see anything clearly specifying this in the documentation.
This is best done by using the script function with an incorrect parameter list, running the script, and observing the error output:
I read in the documentation that one can write a rule
syntax Exp ::= randBounded(Int, Int)
rule randBounded(M, N) => I
requires M <=Int I andBool I <=Int N
[unboundVariables(I)]
I would like randBounded(4,6) to return some random integer. However, when I try it, it returns an integer V0 and sets constraints V0 <=Int 10 ==K true.
Is there a way, instead, to generate explicit branches for every integer in a range?
e.g. I would like to have --search produce 3 configurations:
One for each Integer 4, Integer 5 and Integer 6.
Unfortunately, the expansion you suggest is not possible with --search so you cannot get the exact three configurations. However, if you don't actually need those precise configurations, but instead want to be able to reason on their properties, performing (symbolic) execution (using the haskell backend) using this rule somehow comprises all three configurations.
I am trying to make a plot of a simple mutation accumulation process on a binary tree...
My technical problem in gnuplot, is that is that I want to plot the possibility of getting 2 mutations on a specific lineage on the graph, here is the equation which determines it:
P_{2 mutation} = sum[k=0:n] (m/(2**(k+1)/(1-(1/2)**k)))(1-exp(-muk))
(dont bother with the formula im not sure that this is the correct one yet :))
where n is the number of levels of the binary tree, mu is the mutation rate, and m is the number of previously randomly thrown mutations onto the graphs edges...
I want to make a plot which is this possibility depending on the levels of the binary tree...
Therefore I wrote a script which is something like this:
set term pngcairo size 800,600
set title "Két mutáció megjelenésének valószínűsége, egy n szintű bináris fa egyik sejtvonalában"
set xlabel"szintek száma (n)"
set ylabel"Két mutáció megjelenésének valószínűsége (P_{2^{lin})"
set xrange[1:10]
set yrange[0:1]
set output '2mutvalsz.png'
set multiplot
do for[i=1:10]{
mu = 0.1+(i*0.1)
m = 4
f(x)=(x/((2**(x+1))*(1-(0.5)**x)))
if(m<floor(f(x)))
{
p(x)=sum [k=0:floor(x)](m*(1/((2**(x+1))*(1-(0.5)**x))))*(1-exp(-mu*k))
}
else
{
p(x)=1
}
plot p(x) lt i lw 1
}
unset multiplot
set output
So my problem is, that I dont know if it is correct to do what I do in the
if statement...
What I want is to behold the statement m< f(x) where f(x) is the number of edges in respect of n, which is an integer value therefore I use floor(f(x)), and sum through the x values (which are the number of levels what has to be an integer too... so floor(x), like a heavyside function to make the x axis discrete) in the sum...
And also I get an error message:
gnuplot> load '2mutvalsz.plt'
line 27: undefined variable: x
where line 27 is the end of the do for loop...
So my question is that is it a correct way to make a summation integer the x values and of course why I get the error message...
Thank you, and I hope everything is clear...
The error message is produced because the if statement in your script is interpreted when Gnuplot loads the script - it tries to evaluate the condition of the if statement and since the variable x is not defined, it produces the mentioned message.
You could put everything together using the ternary operator as:
p(x)=( m<floor(f(x)) )?( sum [k=0:floor(x)](m*(1/((2**(x+1))*(1-(0.5)**x))))*(1-exp(-mu*k)) ):1;
However, since the function f(x) is on the imposed x-range of [0,1] less than 1, the condition m<floor(f(x)) will be always false.
I am new to Z notation,
Lets say I have a function f defined as X |--> Y ,
where X is string and Y is number.
How can I get highest Y value in this function? Does 'loop' exist in formal method so I can solve it using loop?
I know there is recursion in Z notation, but based on the material provided, I only found it apply in multiset or bag, can it apply in function?
Any extra reference application of 'loop' or recursion application will be appreciated. Sorry for my English.
You can just use the predefined function max that takes a set of integers as input and returns the maximum number. The input values here are the range (the set of all values) of the function:
max(ran(f))
Please note that the maximum is not defined for empty sets.
Regarding your question about recursion or loops: You can actually define a function recursively but I think your question aims more at a way to compute something. This is not easily expressed in Z and this is IMO a good thing because it is used for specifications and it is not a programming language. Even if there wouldn't be a max or ran function, you could still specify the number m you are looking for by:
\exists s:String # (s,m):f /\
\forall s2:String, i2:Z # (s2,i2):f ==> i2 <= m
("m is a value of f, belonging to an s and all other values i2 of f are smaller or equal")
After getting used to the style it is usually far better to understand than any programming language (except your are trying to describe an algorithm itself and not its expected outcome).#
Just for reference: An example of a recursive definition (let's call it rmax) for the maximum would consist of a base case:
\forall e:Z # rmax({e}) = e
and a recursive case:
\forall e:Z; S:\pow(Z) #
S \noteq {} \land
rmax({e} \cup S) = \IF e > rmax(S) \THEN e \ELSE rmax(S)
But note that this is still not a "computation rule" of rmax because e in the second rule can be an arbitrary element of S. In more complex scenarios it might even be not obvious that the defined relation is a function at all because depending on the chosen elements different results could be computed.