I want to have the possibility to stop a function launched by a button by pushing an other button. More precisely, I want to stop a while loop by changing a parameter :
stop=%F
while ... & stop<>%T
...
end
I tried to write a callback function that change a variable to stop the while :
function callback(handles)
stop=%T
end
but the action isn't triggered before the end of the previous one.
I guess there must be something to do with some threads but i don't have this knowledge in scilab.
You have two solutions. The first one with a prioritary expression callback:
b = uicontrol("style","pushbutton","callback","stop=%t","callback_type",10);
stop = %f;
while ~stop
sleep(1)
end
the second one with a prioritary function callback:
function fun()
stop = %t;
stop = resume(stop);
end
b = uicontrol("style","pushbutton","callback","fun","callback_type",12);
stop = %f;
while ~stop
sleep(1)
end
In the second case you have to use resume to return the local variable stop in the main workspace. Making callback prioritary is a must to interrupt waiting loops.
Related
I'm new to elixir, I'm trying to find something similar to Python's ContextManager.
Problem:
I have a bunch of functions and I want to add latency metric around them.
Now we have:
def method_1 do
...
end
def method_2 do
...
end
... more methods
I'd like to have:
def method_1 do
start = System.monotonic_time()
...
end = System.monotonic_time()
emit_metric(end-start)
end
def method_2 do
start = System.monotonic_time()
...
end = System.monotonic_time()
emit_metric(end-start)
end
... more methods
Now code duplication is a problem
start = System.monotonic_time()
...
end = System.monotonic_time()
emit_metric(end-start)
So what is a better way to avoid code duplication in this case? I like the context manager idea in python. But now sure how I can achieve something similar in Elixir, thanks for the help in advance!
In Erlang/Elixir this is done through higher-order functions, take a look at BEAM telemetry. It is an Erlang and Elixir library/standard for collecting metrics and instrumenting your code - it is widely adopted by Pheonix, Ecto, cowboy and other libraries. Specifically, you'd be interested in :telemetry.span/3 function as it emits start time and duration measurements by default:
def some_function(args) do
:telemetry.span([:my_app, :my_function], %{metadata: "Some data"}, fn ->
result = do_some_work(args)
{result, %{more_metadata: "Some data here"}}
end)
end
def do_some_work(args) # actual work goes here
And then, in some other are of your code you listen to those events and log them/send them to APM:
:telemetry.attach_many(
"test-telemetry",
[[:my_app, :my_function, :start],
[:my_app, :my_function, :stop],
[:my_app, :my_function, :exception]],
fn event, measurements, metadata, config ->
# Handle the actual event.
end)
nil
)
I think the closest thing to python context manager would be to use higher order functions, i.e. functions taking a function as argument.
So you could have something like:
def measure(fun) do
start = System.monotonic_time()
result = fun.()
stop = System.monotonic_time()
emit_metric(stop - start)
result
end
And you could use it like:
measure(fn ->
do_stuff()
...
end)
Note: there are other similar instances where you would use a context manager in python that would be done in a similar way, on the top of my head: Django has a context manager for transactions but Ecto uses a higher order function for the same thing.
PS: to measure elapsed time, you probably want to use :timer.tc/1 though:
def measure(fun) do
{elapsed, result} = :timer.tc(fun)
emit_metric(elapsed)
result
end
There is actually a really nifty library called Decorator in which macros can be used to "wrap" your functions to do all sorts of things.
In your case, you could write a decorator module (thanks to #maciej-szlosarczyk for the telemetry example):
defmodule MyApp.Measurements do
use Decorator.Define, measure: 0
def measure(body, context) do
meta = Map.take(context, [:name, :module, :arity])
quote do
# Pass the metadata information about module/name/arity as metadata to be accessed later
:telemetry.span([:my_app, :measurements, :function_call], unquote(meta), fn ->
{unquote(body), %{}}
end)
end
end
end
You can set up a telemetry listener in your Application.start definition:
:telemetry.attach_many(
"my-app-measurements",
[[:my_app, :measurements, :function_call, :start],
[:my_app, :measurements, :function_call, :stop],
[:my_app, :measurements, :function_call, :exception]],
&MyApp.MeasurementHandler.handle_telemetry/4)
nil
)
Then in any module with a function call you'd like to measure, you can "decorate" the functions like so:
defmodule MyApp.Domain.DoCoolStuff do
use MyApp.Measurements
#decorate measure()
def awesome_function(a, b, c) do
# regular function logic
end
end
Although this example uses telemetry, you could just as easily print out the time difference within your decorator definition.
I am working with a program which includes many function calls inside a for loop. For short, it is something like this:
function something()
....
....
timer = zeros(NSTEP);
for it = 1:NSTEP # time steps
tic = time_ns();
Threads.#threads for p in 1:2 # Star parallel of two sigma functions
Threads.lock(l);
Threads.unlock(l);
arg_in_sig[p] = func_sig[p](arg_in_sig[p]);
end
.....
.....
Threads.#threads for p in 1:2
Threads.lock(l)
Threads.unlock(l)
arg_in_vel[p] = func_vel[p](arg_in_vel[p])
end
toc=time_ns();
timer[i] = toc-tic;
end # time loop
writedlm("timer.txt",timer)
return
end
What I am trying to do, is to meassure the time that takes to perform on each loop iteration, saving the result in an output file called "timer.txt". The thing is that it doesn't work.
It saves a file with all zeros on it (except two or three values, which is more confusing).
I made a toy example like:
using DelimitedFiles;
function test()
a=zeros(1000)
for i=1:1000
tic = time_ns();
C = rand(20,20)*rand(20,20);
toc = time_ns();
a[i] = toc-tic;
end
writedlm("aaa.txt",a);
return a;
end
and these actually works (it saves fine!). Is there something to do with the fact that I am implementing Threads.#threads?. What can be happening between writedlm() and time_ns() in my program?
Any help would be much apreciated!
You are iterating over it but try to save by:
timer[i] = toc-tic;
while it should be
timer[it] = toc-tic;
Perhaps you have some i in global scope and hence the code still works.
Additionally locking the thread and immediately unlocking does not seem to make much sense. Moreover, when you iterate over p which happens to be also index of the Vector cell where you save the results there is no need to use the locking mechanism at all (unless you are calling some functions that depend on a global state).
Is a loop.close() needed prior to returning async values in the below code?
import asyncio
async def request_url(url):
return url
def fetch_urls(x):
loop = asyncio.get_event_loop()
return loop.run_until_complete(asyncio.gather(*[request_url(url) for url in x]))
That is, should fetch_urls be like this instead?:
def fetch_urls(x):
loop = asyncio.get_event_loop()
results = loop.run_until_complete(asyncio.gather(*[request_url(url) for url in x]))
loop.close()
return results
If the loop.close() is needed, then how can fetch_urls be called again without raising the exception: RuntimeError: Event loop is closed?
A previous post states that it is good practice to close the loops and start new ones however it does not specify how new loops can be opened?
You can also keep the event loop alive, and close it the end of your program, using run_until_complete more than once:
import asyncio
async def request_url(url):
return url
def fetch_urls(loop, urls):
tasks = [request_url(url) for url in urls]
return loop.run_until_complete(asyncio.gather(*tasks, loop=loop))
loop = asyncio.get_event_loop()
try:
print(fetch_urls(loop, ['a1', 'a2', 'a3']))
print(fetch_urls(loop, ['b1', 'b2', 'b3']))
print(fetch_urls(loop, ['c1', 'c2', 'c3']))
finally:
loop.close()
No, the async function (request in this case) should not be closing the event loop. The command loop.run_until_complete will close stop the event loop as soon as it runs out of things to do.
fetch_urls should be the second version -- that is, it will get an event loop, run the event loop until there is nothing left to do, and then closes it loop.close().
I am trying to move the mouse every 2 minutes so that the session doesn't time out. But despite no syntax errors, it doesn't work.
My code:
global $x = 1
global $y = 1
If Mod(#MIN, 3) = 0 Then
MouseMove (global $x, global $y, 2)
global $x++
global $y++
endif
Its more usefull to perform a callback function for timed calls.
AdlibRegister('_MouseMove', 2000*60) ; calls the function every 2000*60 ms
OnAutoItExitRegister('_UnRegister') ; unregister the callback function when the script ends
Func _MouseMove()
Local $aPos = MouseGetPos()
; move 1px right and back after a short brake - so that your interface can detect the movement
MouseMove($aPos[0]+1, $aPos[1])
Sleep(50)
MouseMove($aPos[0], $aPos[1])
EndFunc
Func _UnRegister()
AdlibUnRegister('_MouseMove')
EndFunc
Btw.: Increasing values with AutoIt works so
$x += 1
Edit:
I'm not sure, if you want 2 or 3 minutes (you've written both). So you can change it in the time parameter in AdlibRegister(). The interval must given in ms.
When you run your script in SciTE you should see the following error message:
You need the global keyword only when declaring a variable. When using a variable you have to ommit the global keyword. You should change your script accordingly and it might work then.
The following script move the mouse one pixel every 3 minutes, preventing the session time out, with minimal impact on the computer usage.
HotKeySet( "{ESC}" , "Sair")
While True
MouseMove(MouseGetPos(0)+1,MouseGetPos(1))
Sleep(180000)
MouseMove(MouseGetPos(0)-1,MouseGetPos(1))
Sleep(180000)
WEnd
Func Sair()
Exit
EndFunc
In a classic ASP function, when I do a loop inside another as shown in the code below I have a stack overflow error.
Function shift(x,y)
shift = x
For i = 1 to y
shift = shift*2
Next
End Function
Function translate_url(iVal)
sAlpha = "abcdefghijklmnopqrstuvwxyz-_0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
doWrite = False
iBase = 63 'DO NOT CHANGE
For i = 4 to 0 step -1
iPos = (iVal and shift(iBase, i*6))/shift(1, i*6)
If iPos Then doWrite = True
If doWrite Then translate_url = translate_url & Mid(sAlpha, iPos + 1,1)
Next
End Function
arr = Split("1,2,3,4,5,6,7,8,9,0",",")
For Each i In arr
response.Write(translate_url(arr(i)))
next
The error does not occur when I remove the loop outside the function. Eg:
response.Write(translate_url(arr(1)))
return "c".
What I need to do to make the code flows down the array and return the corresponding values according to the function?
VBScript has a dark side. Variables scope is one of them.
When you don't declare a variable, VBScript will do it for you, free of charge or error and give it global scope.
What does it mean? Take a look in the main loop:
For Each i In arr
response.Write(translate_url(arr(i)))
next
The i variable becomes global. When you have this later in the function:
For i = 4 to 0 step -1
'...
Next
It's changing the same i variable. This is causing endless loop of function calls.
To resolve this, declare i locally in each function:
Function shift(x,y)
Dim i
'...
End Function
Function translate_url(iVal)
Dim i
'...
End Function
And it will be different variable and no overflow.
As the EVIL global variable i is used in your top level loop and in the functions shift() and translate_url(), you got what you deserve.
Evidence: Just change your loop to
For Each NoliMeTangere In arr
response.Write translate_url(arr(NoliMeTangere))
next
Remedy: Use "Option Explicit" and Dim all local variables in your Subs/Functions/Methods.