i have an array S[1,4,2,3,0] of index[1,2,3,4,5] and an array O[2,1,1,2] of index [1,2,3,4], from these two i have to generat an array SO[2,2,1,1,0] of index [1,2,3,4,5]. When i run with constraint forall(i in 1..5)(SO[i] = O[S[i]]); i get error unsatisfied because of no index 0 for O. Please Help me out with this i am new to minizinc and i dont find sufficient material to help
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constraint forall(i in 1..5)(SO[i] = O[S[i]]);`i/p array S[1,4,2,3,0] of index[1,2,3,4,5];
The problem with your model is that S[5] is 0 (zero) and there no corresponding SO[0].
I'm not sure if you thought that MiniZinc would automatically yield a 0 if the value of O[0] is missing, but MiniZinc requires that you are explicit about the indices in an array when it don't start at 1.
You can fix this by adding an index of 0 (zero) in the O array, together with array1d:
array[1..5] of int: S = [1,4,2,3,0];
array[0..4] of int: O = array1d(0..4,[0,2,1,1,2]); # <---
array[1..5] of var 0..2: SO;
solve satisfy;
constraint forall(i in 1..5) (
SO[i] = O[S[i]]
);
The result is:
SO = array1d(1..5 ,[2, 2, 1, 1, 0]);
Related
This seems like such a simple problem, but I can't find a simple way to represent this in MiniZinc.
include "globals.mzn";
int: target;
int: max_length;
var 1..max_length: length;
array[1..length] of int: t;
constraint sum(t) = target;
constraint alldifferent(t);
solve minimize length;
This program errors with:
MiniZinc: type error: type-inst must be par set but is ``var set of int'
Is there a clean/simple way to represent this problem in MiniZinc?
Arrays in MiniZinc have a fixed size. The compiler is therefore saying that array[1..length] of int: t is not allowed, because length is a variable.
The alternative that MiniZinc offers is arrays with optional types, these are values that might exist. This means that when you write something like [t | t in 1..length], it will actually give you an array of 1..maxlength, but some elements can be marked as absent/<>.
For this particular problem you are also overlooking the fact that t should itself be a array of variables. The values of t are not yet known when at compile-time. A better way to formulate this problem would thus be to allow the values of t to be 0 when they are beyond the chosen length:
include "globals.mzn";
int: target;
int: max_length;
var 1..max_length: length;
array[1..max_length] of var int: t;
constraint sum(t) = target;
constraint alldifferent_except_0(t);
constraint forall(i in length+1..max_length) (t[i] = 0);
solve minimize length;
The next step to improve the model would be to ensure that the initial domain of t makes sense and instead of being all different, forcing an ordering would be equivalent, but eliminate some symmetry in the possible solutions.
I have a table with features = {A,B}. B is a column of integers. Scanning the table, when I have a value change in B column, I increment a variable "changes" of 1:
if data[i,B]!=data[i-1,B]
then changes=changes+1
I want to find an order that minimizes changes and at the same time keep the repetition of a value in B in [0,upper_bound].
I'm thinking to use an array as a decision variable where save the position j for the element i:
order[i]=j means i element in data is the j-th element in ordering.
How can I model with constraint? This is what I do until now:
array[1..n, Features] of int: data;
int: changes=0;
constraint
forall(i in 1..n) (
if data[i,B] != data[i-1,B] then
changes=changes+1
endif
)
;
minimize changes;
I think I'm wrong using changes as a constant variable, right? Thank you in advance.
In MiniZinc (and in constraint programming in general) you cannot increment a variable as changes=changes+1).
If changes is a variable used only for the total count of changes you can use sum instead, something like:
% ...
var 0..n: num_changes;
constraint
changes = sum([data[i,B] != data[i-1,B] | i in 2..n])
;
% ...
However, if you want to use the number of accumulated changes for each i then you have to create a changes array to collect the values for each step, e.g.
var[1..n-1] of var 0..n: changes;
% the total number of changes (to minimize)
var 0..n-1: total_changes = changes[n-1];
constraint
forall(i in 1..n-1) (
if data[i,B] != data[i-1,B] then
changes[i] = changes[i-1]+1
else
changes[i] = changes[i-1]
endif
)
;
include "globals.mzn";
%Data
time_ID = [11,12,13,14,15];
eventId = [0011, 0012, 0013, 0021, 0022, 0031, 0041, 0051, 0061, 0071];
int:ntime = 5;
int:nevent = 10;
set of int: events =1..nevent;
set of int: time = 1..ntime;
array[1..nevent] of int:eventId;
array[1..nevent] of var time:event_time;
array[1..ntime] of int:time_ID;
solve satisfy;
constraint
forall(event in eventId)(
exists(t in time_ID)(
event_time[event] = t ));
output[ show(event_time) ];
I'm trying to assign times to an event using the code above.
But rather than randomly assign times to the events, it returns an error " array access out of bounds"
How can I make it select randomly from the time array?
Thank you
The error was because you tried to assign the index 11 (the first element in eventId array) in "event_time" array.
The assigment of just 1's is correct since you haven't done any other constraints on the "event_time" array. If you set the number of solutions to - say - 3 you will see other solutions. And, in fact, the constraint as it stand now is not really meaningful since it just ensures that there is some assignment to the elements in "event_time", but this constraint is handled by the domain of "event_time" (i.e. that all indices are in the range 1..ntime).
As simple as in title. I have nx1 sized vector p. I'm interested in the maximum value of r = p/foo - floor(p/foo), with foo being a scalar, so I just call:
max_value = max(p/foo-floor(p/foo))
How can I get which value of p gave out max_value?
I thought about calling:
[max_value, max_index] = max(p/foo-floor(p/foo))
but soon I realised that max_index is pretty useless. I'm sorry asking this, real beginner here.
Having dropped the issue to pieces, I realized there's no unique corrispondence between values p and values in my related vector p/foo-floor(p/foo), so there's a logical issue rather than a language one.
However, given my input data, I know that the solution is unique. How can I fix this?
I ended up doing:
result = p(p/foo-floor(p/foo) == max(p/foo-floor(p/foo)))
Looks terrible, so if you know any other way...
Once you have the index, use it:
result = p(max_index)
You can create a new vector with your lets say "transformed" values:
p2 = (p/foo-floor(p/foo))
and then just use find to find the max values on p2:
max_index = find(p2 == max(p2))
that will return the index or indices of p2 with the max value of that operation, and finally just lookup the original value in p
p(max_index)
in 1 line, this is:
p(find((p/foo-floor(p/foo) == max((p/foo-floor(p/foo))))))
which is basically the same thing you did in the end :)
I have a struct, that's a <1x1 struct>, and I'm trying to edit a field in the struct based on the values. The field is called GeoDist_Actual and the struct is called GeoDist_str. The field GeoDist_Actual is a <262792x1 double>, and this is the code I was trying to use in order to get rid of the values that are greater than 1.609344e+05.
i =1;
for i=i:size(GeoDist_str.GeoDist_Actual)
if GeoDist_str.GeoDist_Actual(i,1 > 1.609344e+05
GeoDist_str.GeoDist_Acutal(i,1) = [];
end
end
How would I append or alter this code in order to make it function like I'm aiming? I considered setting all the values to 0, but I'm going to have to go backwards from this in order to get back GPS values, doing a reverse-Vincenty(spherical) calculation, and I'd like to just completely get rid of the values that don't comply with the if condition.
If I can narrow down the question at all, let me know, and thank you for your help in advance!
Edit: I've noticed that when I changed out the section
GeoDist_str.GeoDist_Actual(i,1) = [];
for
GeoDist_str.GeoDist_Actual(i,1) = 0;
It didn't actually solve anything, instead it didn't access the field "GeoDist_Actual" within the struct "GeoDist_str", it just created a mirror field with values of 0.
Consider this example:
% a 10-by-1 vector
x = [1;2;3;4;5;6;7;8;9;10];
% remove entries where the value is less than five
x(x<5) = [];
This is called logical indexing, no need for loops.
Consider the following simple example:
A.a = 1:5;
A =
a: [1 2 3 4 5]
now delete all elements bigger 3;
A.a = A.a( ~(A.a > 3) );
A =
a: [1 2 3]
or alternatively:
A.a( A.a > 3 ) = []
For your case it's a little more bulky:
GeoDist_str.GeoDist_Actual = ...
GeoDist_str.GeoDist_Actual( ...
~(GeoDist_str.GeoDist_Actual > 1.609344e+05) )