I'm working on a project related with AC OPF (Optimal Power Flow) and I was trying to solve a problem in python, using pyomo.
There are 3 buses and the bus voltage and bus angle are limited. However, the 1st bus must have a voltage=1 and an angle=0.
So, I tried this:
model.busvoltage = Var(model.bus, initialize=1, bounds=(0.95, 1.05), doc='Bus Voltage')
model.busvoltage[1].fixed=True
model.busangle = Var(model.bus, initialize=0, bounds=(-3.14, 3.14), doc='Bus angle')
model.busangle[1].fixed=True
The problem is that I just want to set the busvoltage and busangle for the first bus, without initializing the other ones with those values. I don't know if this is important to write, but I'm using ipopt as solver.
(This is my first time programming in Python) Any help would be appreciated!
You're after the .value attribute of the variable. Furthermore, setting the value of a variable and fixing it at the same time can be simplified to calling .fix():
model.busvoltage = Var(model.bus, bounds=(0.95, 1.05), doc='Bus Voltage')
model.busvoltage[1].fixed = True
model.busvoltage[1].value = 1
model.busangle = Var(model.bus, bounds=(-3.14, 3.14), doc='Bus angle')
model.busangle[1].fix(0)
Have you considered initializing the value in a constraint rather than in the Var definition?
model.busvoltage = Var(model.bus, bounds=(0.95, 1.05), doc='Bus Voltage')
model.busvoltage[1].fixed=True
def bus_voltage_1_value_constraint(model, b):
if b == 1:
return model.busvoltage[b] == 1
return Constraint.Skip
model.bus_voltage_1_value = Constraint(model.bus, rule=bus_voltage_1_value_constraint)
Related
I'm working with the ipaddress module in Python and trying to figure out a way of calculating the next available subnet (of either the same prefix or a different prefix) that doesn't overlap the existing subnet (the new subnet MUST be greater than the old one).
Lets say I start with network:
from ipaddress import IPv4Network
# From 10.90.1.0 to 10.90.1.31
main_net = IPv4Network("10.90.1.0/27")
I know the next available address is going to be 10.90.1.32, I can even figure this out quite easily by doing:
next_ip = main_net.broadcast_address + 1
# will output 10.90.1.32
print(next_ip)
If I wanted to find the next /27, I just create a new network like so:
# From 10.90.1.32 to 10.90.1.63
new_net = IPv4Network(f"{next_ip}/27")
This is all very straightforward so far, but now what if the next subnet I am looking for is a /26 or a /28 - how can I find the next minimum start IP address for either of these cases in Python?
I have explored using the supernet method, for example I could do something like this:
# Will print 10.90.1.0/26
print(main_net.supernet(new_prefix=27))
The problem with this method is that it will print 10.90.1.0/26 which overlaps the existing 10.90.1.0/27 network, I could make a loop and get it to keep generated the next /26 until they stop overlapping, but it seems inefficient to me. Surely, there is a better way?
Thanks to the help of Ron Maupin's helpful comment leading to a useful guide, I have managed to make a function that does this. I still want to test it a bit more but believe it is correct:
def calculate_next_ip_network(ip_bytes, current_prefix, next_prefix):
next_prefix_mask = (~((1 << (32 - next_prefix)) - 1)) & 0xFFFFFFFF
if next_prefix <= current_prefix:
bit_shift = 32 - next_prefix
else:
bit_shift = 32 - current_prefix
new_ip = (((next_prefix_mask & ip_bytes) >> bit_shift) + 1) << bit_shift
return bytes([new_ip >> i & 0xFF for i in (24, 16, 8, 0)])
Usage:
nt = IPv4Network("10.90.1.56/29")
current_prefix = nt.prefixlen
next_prefix = 25
ip_bytes = int.from_bytes(nt.network_address.packed, byteorder="big")
next_ip = calculate_next_ip_network(ip_bytes, current_prefix, next_prefix)
print(IPv4Address(next_ip))
# Should print "10.90.1.128"
can anyone enlighten me why the following modelica code generates an error on OpenModelica 1.12.0? If I remove the last two connect equations, it works fine.
class A
Conn cc[3];
Real a(start=0,fixed=true);
Real b(start=0,fixed=true);
Real c(start=0,fixed=true);
equation
der(a) = 1;
der(b) = 2;
der(c) = 3;
connect(a,cc[1].v);
connect(b,cc[2].v); // Remove this to make it work
connect(c,cc[3].v); // Remove this to make it work
end A;
The expandable connector cc is empty:
expandable connector Conn
end Conn;
The code above generates error on OpenModelica 1.12.0:
[1] 15:07:44 Symbolic Error
Too many equations, over-determined system. The model has 6 equation(s) and 4 variable(s).
[2] 15:07:44 Symbolic Warning
[A: 11:3-11:21]: Equation 5 (size: 1) b = cc[2].v is not big enough to solve for enough variables.
Remaining unsolved variables are:
Already solved: b
Equations used to solve those variables:
Equation 2 (size: 1): der(b) = 2.0
[3] 15:07:44 Symbolic Warning
[A: 12:3-12:21]: Equation 6 (size: 1) c = cc[3].v is not big enough to solve for enough variables.
Remaining unsolved variables are:
Already solved: c
Equations used to solve those variables:
Equation 3 (size: 1): der(c) = 3.0
Basically, I want to have an array of expandable connectors which I can add different type of variables as needed.
Edit 18/08/2018
Regarding I can only connect the "connectors" to an expandable connector, actually I see the modelica spec 3.4 doc says:
All components in an expandable connector are seen as connector instances even if they are not declared as
such [i.e. it is possible to connect to e.g. a Real variable].
So it seems I can connect Real variables to an expandable connector in OpenModelica however, I get an error in JModelica:
Error at line 13, column 11, in file 'A.mo':
Connecting to an instance of a non-connector type is not allowed
Also I can connect Real variables to normal (non-expandable) connectors as well in OpenModeica, but again this is not allowed in JModelica. So tools interpret the language specs differently!
You cannot connect Real variables to the expandable connector, it needs to be connectors. But somehow that doesn't work either, seems to be a bug. What works (tested in OM and Dymola) is this below:
class Expandable
expandable connector Conn
Real v[3];
end Conn;
connector RealOutput = output Real "'output Real' as connector";
Conn cc;
RealOutput a(start=0,fixed=true);
RealOutput b(start=0,fixed=true);
RealOutput c(start=0,fixed=true);
equation
der(a) = 1;
der(b) = 2;
der(c) = 3;
connect(a,cc.v[1]);
connect(b,cc.v[2]);
connect(c,cc.v[3]);
end Expandable;
I'm trying to connect two blocks with the "Connector" class implemented in pyomo, using the following simple examplary code.
from pyomo.environ import *
m = ConcreteModel()
# Block 01
m.block_01 = Block()
m.block_01.flow = Var(within=NonNegativeReals, bounds=(2, 10))
m.block_01.OUT = Connector(initialize= {'flow': m.block_01.flow})
# Block 02
m.block_02 = Block()
m.block_02.flow = Var(within=NonNegativeReals)
m.block_02.IN = Connector(initialize= {'flow': m.block_02.flow})
m.con = Constraint(expr=m.block_01.OUT == m.block_02.IN)
def _obj(_m):
return _m.block_01.flow + _m.block_02.flow
m.obj = Objective(rule=_obj)
After "optimization" all variables take their lower bound values (m.block_01.flow = 2 and m.block_02.flow = 0). So the Connector seems not to transfer any data for the variables.
If I'm using:
m.con = Constraint(expr=m.block_01.flow == m.block_02.flow)
instead, it works. However this is not the idea of Connectors, right?
Any ideas about the reason for the problem?
Did you apply the expand_connectors transformation before sending your model to a solver?
TransformationFactory('core.expand_connectors').apply_to(m)
I am using a data frame to create a marked point process using as.ppp function. I get an error Error: is.numeric(x) is not TRUE. The data I am using is as follows:
dput(head(pointDataUTM[,1:2]))
structure(list(POINT_X = c(439845.0069, 450018.3603, 451873.2925,
446836.5498, 445040.8974, 442060.0477), POINT_Y = c(4624464.56,
4629024.646, 4624579.758, 4636291.222, 4614853.993, 4651264.579
)), .Names = c("POINT_X", "POINT_Y"), row.names = c(NA, -6L), class = c("tbl_df",
"tbl", "data.frame"))
I can see that the first two columns are numeric, so I do not know why it is a problem.
> str(pointDataUTM)
Classes ‘tbl_df’, ‘tbl’ and 'data.frame': 5028 obs. of 31 variables:
$ POINT_X : num 439845 450018 451873 446837 445041 ...
$ POINT_Y : num 4624465 4629025 4624580 4636291 4614854 ...
Then I also checked for NA, which shows no NA
> sum(is.na(pointDataUTM$POINT_X))
[1] 0
> sum(is.na(pointDataUTM$POINT_Y))
[1] 0
When I tried even only the first two columns of the data.frame, the error I get on using as.ppp is this:
Error: is.numeric(x) is not TRUE
5.stop(sprintf(ngettext(length(r), "%s is not TRUE", "%s are not all TRUE"), ch), call. = FALSE, domain = NA)
4.stopifnot(is.numeric(x))
3.ppp(X[, 1], X[, 2], window = win, marks = marx, check = check)
2.as.ppp.data.frame(pointDataUTM[, 1:2], W = studyWindow)
1.as.ppp(pointDataUTM[, 1:2], W = studyWindow)
Could someone tell me what is the mistake here and why I get the not numeric error?
Thank you.
The critical check is whether PointDataUTM[,1] is numeric, rather than PointDataUTM$POINT_X.
Since PointDataUTM is a tbl object, and tbl is a function from the dplyr package, what is probably happening is that the subset operator for the tbl class is returning a data frame, and not a numeric vector, when a single column is extracted. Whereas the $ operator returns a numeric vector.
I suggest you convert your data to data.frame using as.data.frame() before calling as.ppp.
In the next version of spatstat we will make our code more robust against this kind of problem.
I'm on the phone, so can't check but I think it is happens because you have a tibble and not a data.frame. Please try to convert to a data.frame using as.data.frame first.
I am trying to find the data between two values. I am using this code in a GUI programme, the starting_value and ending_value which you can see in the code below are selected from 2 listboxes in a previous part of the code.
% --- Executes on button press in CalculateIntensity.
function CalculateIntensity_Callback(hObject, eventdata, handles)
% hObject handle to CalculateIntensity (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Trapz function
starting_value = getappdata(0,'StartValue');
ending_value = getappdata(0,'EndValue');
StartingValue = str2mat(starting_value)
EndingValue = str2mat(ending_value)
A = getappdata(0,'XYarray')
data_found = A(A(:,[1,2]) > StartingValue & A(:,[1,2]) < EndingValue)
I found help on:
http://www.mathworks.com/matlabcentral/answers/8556-how-to-find-vector-elements-between-two-values-efficiently
However the
data_found = A(A(:,[1,2]) > StartingValue & A(:,[1,2]) < EndingValue)
part of the code wont work for me, I think starting_value and ending_value are strings so I tried converting it to a matrix but I get the error:
Error using <
Matrix dimensions must agree.
Error in MichelleLaycockGUImainwindow>CalculateIntensity_Callback (line 119)
data_found = A(A(:,[1,2]) > StartingValue & A(:,[1,2]) < EndingValue)
an example of data used is:
A =
1.0e+03 *
0.1660 1.1570
0.1664 0.4650
0.1668 0
0.1672 1.0200
0.1676 1.0110
0.1680 1.0200
0.1684 1.0640
0.1688 1.1100
0.1692 1.0370
0.1696 1.0050
0.1700 1.0750
0.1704 1.0850
0.1708 1.1310
0.1712 1.0630
0.1716 1.0370
0.1719 1.1070
0.1724 1.1450
I'm not really sure where I'm going wrong, any help would be greatly appreciated as it's all I need to complete my work. Thanks in advance!
As some of the values in my data vary rather than just decreasing or increasing the greater than or equal to method I was originally trying to use did not work. So rather than using the loop to get the data between the two points selected I went with a different method.
I use[~,indx1]=ismember(StartingValue,A,'rows') this finds the row number of the selected data and then I use this information to extract the data between and including the selected data.
Here is the full code I used to do this:
starting_value = getappdata(0,'StartValue');
ending_value = getappdata(0,'EndValue');
StartingValue = str2num(starting_value);
EndingValue = str2num(ending_value);
A = getappdata(0,'XYarray');
[~,indx1]=ismember(StartingValue,A,'rows');
[~,indx2]=ismember(EndingValue,A,'rows');
arrayfortrapz = A(indx1:indx2,1:2); %array of data including and between selected data
I hope this of some help to anybody that may run into a similar issue.