Delays in parallel before loop



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Similar Questions

  • parallel for loops does not

    Hello.

    I'm learning the multi - thread programming. To start, I use "parallel for loops" and I was surprised that it does not work. One - thread loop work a few times faster (depending on settings) that multi - thread. I don't know why, and it is my request to correct my Vi to work properly.

    Lenovo, G580, Windows 7, 64-bit computer

    Intel Core i7 3632QM
    Ivy Bridge
    Specification Intel (r) Core i7-3632QM CPU @ 2.20 GHz
    Package (platform ID) Socket 988 B rPGA (0x4)
    Number of hearts 4
    Number of threads 8

    LabView 2011.

    Altenbach says:

    Gibbon wrote:

    What was 'strange' behavior?  In "linia dluga" when inside the loop is on '1' of the "spreed up' between one and multi-fil is about 3 times, when I put it in '20' this grow to 6.2. It was strange form me, becourse I expect a similar value.

    A parallel FOR loop has an overhead for parallelization (split the problem, then go back the results, etc.). If the code is very fast, the overhead is proportionally larger. If the Subvi takes a long time to complete, the overhead of parallelization is insignificant. It is often not worthwhile to parallelize the loops with a very simple and fast code.

    Gibbon wrote:

    Altenbach - I have another question if you can help me - how did you "seconds relative high resolution." VI "? -I want to say how did you know that there is this 'vi '. And thanks a lot for your modyfications.

    You can find it in vi.lib\utilities. It is well known.

    Maybe not well known enough!  the 'Hidden gems' package adds to your palattes.  It has also been considered by a nugget of the community

  • Préallouée VI environment in paralleled for loop

    Hello

    I searched a bit and couldn't find that everything about this specific issue.

    If I have a Subvi in a parallelized for loop and the Subvi is set upon reentrant preallouee clone, the Subvi register also several characteristics of memory depending on the number of loop iteration For? My specific application is a Subvi containingvibration Analytisis screw using the previous data in their spread and filters.

    Thank you!


  • LabVIEW parallel for loop and OpenMP

    Hello:

    It's just a curious post, I just learned about OpenMP and I found that OpenMP helps you to parallelize loops in c about the same way that you can use the loop For parallel in LabVIEW.

    The loop For Parallel LabVIEW is being implemented under the hood using OpenMP? Or is it just a coincidence?

    No, it is not implemented LabVIEW parallel for loop under the hood using OpenMP. You might be interested to read this article on modern developments in the LabVIEW compiler architecture. Specifically, in this case, it's the DFIR technology discussed here that facilitates parallel for loop transformations.

  • 2 parallel while loops with functional overall to share data

    Hello

    I'm having a problem with the sharing of functional with globals data between two parallel while loops:

    1. One of the loop (bottom) generates a random number periodically and write the total functional sample.
    2. Another loop (above) has a structure of event and when it expires, he would read the functional global and intrigue, a chart data point.

    The problem is sometimes the functional overall seems to be 'locked' and the output becomes zero constant. It also seems that whenever I first open the VI, it works fine. But for the second time running, he begins to have the problem.

    You must initialize your VI stop FGV FRONT of your lower loop begins.  Even if you use a global variable that is functional, you have a race condition.  FGV is read in the lower loop until it had a chance to be initialized with a value of false in the upper loop.  Functional global variables do not forget their data between executions of the VI.  So it is always set on stop the last time that you ran the VI.  This works your VI the first time it's because VI does not have in memory, so when it loads, it loads with the default value False in the shift register.

  • Parallel for loop 2D table

    Hello

    I don't have any experience with parallel for loops, so I need your help.

    Goal: To do a calculation (average, average) on the rows (or columns) table 2D as quickly as possible. The calculations are independent of each other and I would get a table 1 d with the results.

    I read a few posts on parallel for loops and I would like to find an example for my trivial problem, but I can't.

    Could you help me, it is possible is improve it the effectiveness of the calculation on lines with parallelism in LabVIEW? and it is, could you post an example how to do?

    Thank you

    If the speed issues, do not write your own "average." First of all, it already is in the range of statistics, but then you must be inline your average VI or do the calculation explicitly (as shown below). the size of the array never changes for the duration of the loop, it seems redundant to get the size of the array on each iteration.

    Here's what you could do.

    On my bench, it's much faster than the use of 'mean.vi' of the palette. Average a overhead, Subvi (1) (2) needs to get N with each call and (3) is also an unnecessary error checking.

    (Sorry, I have 32 processors, so the number of instances is set a little high. Modify if needed).

  • How to create parallel tasks using parallel for loops

    Hello

    I'm going to put in place a program that communicates with the six logical controllers and must read the status of the system every 100 Ms. we use OPC datasockets for this, and they appear a bit slow.

    I created a uniform method of comm. for all controllers, and now I find myself this method of programming six times to communicate with each system. I was wondering if it could be done more elegant using the parallel for loop, in which case I program an Exchange once and then six workers running simultaneously. Since a picture is clearer than a thousand words, what I'm asking is:

    Is it possible to replace something like

    by

    and that for performing these tasks in parallel loop (on different cores / in different threads)?

    I have configured the loop to create instances of the 8 to the compilation, so I would 2 surplus available when running instances if I find that I need an additional system.

    The benefits of the Show method in the second photo for me are:

    * takes less space

    * changes need be made only once

    * less blocks, son and other things makes it clearer what is happening.

    * flexibility of the actual number of tasks running (8 available runtime instances)

    * If multiple tasks are necessary, I need only update the maximum number of instances and recompile, i.e. no cutting and pasting necessary.

    Unfortunately, I don't have these available system yet, so there is no way to test this. Yet, I would like to know if the above works as I hope - unfortunately the help of labview is not quite clear to me on that.

    Best regards

    Frans

    Frans, the parallel for loop will work as expected in this situation. The six tasks will run simultaneously in different threads. What part of the aid could be made clearer?

  • Error with parallel while loops

    Hello

    I need to connect 6 different instruments gpib. I am using parallel loops, but the problem is when I try to open 2 or 3 Subvi simultaneously (the intstrument drivers), I just open one because of everything in a loop to run the Subvi. The program should be able to open all the Sub - VI independently.

    Can give you some ideas?

    Thank you

    A. Castillo

    Look at the detailed help for functions to notify.  Then follow the links to the examples included with LV

    Another problem that you have, whether you use your curls greedy or reporting or another technique, is to know how to stop your hand while loop.  All the subVIs must be called before the loop stops.  This is the fundamental paradigm of LV

    You will probably need to rethink your primary architecture to something that will actually do what you want.  Plan and design before your departure from the coding.  Note requirements for the program and determine which parts are dependent on othrer parts, then select a program architecture that can meet the requirements.

    Lynn

  • Waiting for timeouts in parallel for loop

    Hello

    I am currently working on a project where I communicate with a number of devices over TCP. This happens at the same time, which is not a problem as long as does not change the number of devices. Now, I want to open my project to support the case with different numbers of hardware devices, which I want to make a loop (read the device of DB information in an array and iterate over all items).

    I read on a single loop parallel execution for, but it seems that the logical cores is a limiting factor for the number of alternative treatments. Unfortunately, I must also take into account delays in communication which translates as the waiting time for each iteration of the loop.

    As you can see I have this creates a lot of idle time that adds up quickly (running with 10 carrots 4 logic devices takes three times the delay to finish without the loop it would not delay time as all connections are pending at the same time.

    I hope someone can direct me to a solution.

    Thank you

    Move the reference VI opened in the first LOOP.

    You use the same reference for all instances.  So wait for asynchronous call will just see one of them finished and the results.  By placing the reference VI open inside your loop, you will have a different reference for each call of your VI.

  • How to end parallel while loops

    Hi, I'm using LV8.5.  I have 2 while loops, running in parallel.  Loop1 is faster (waiting time of 100 ms) and Loop2 is slower (several minutes waiting time).  I use a local variable (STOP button) Boolean to commonality between the loops.  The button is in the loop faster (Loop1) and the local variable is in Loop2.  When I try to end the While loop, Loop1 stops immediately, while I have to wait for Loop2 finish.  Is there a simple way to make two loops to stop immediately?  I have been using a Control\Stop Application, but may not be the right solution.

    Thank you.

    Hi shanx2,

    reduce waiting time in your second loop and count the iterations instead. The loop will do the same, but the stop will react much faster. Another possibility would be to use a queue instead. Connect to a timeout that corresponds to the current time-out period, you use and send a message to stop the loop. You can choose between the queue has been exceeded or not. Connect this result to the conditional loop. You can send the message from the queue after the first loop was arrested.

    Mike

  • Use of LabView delay in a while loop instead of use the inherent instrument of time loop.

    I have a lmg500 sez I use. It has the possibility of continuous measurement of data, with a cycle of user control loop (always using a while loop but the delay comes from the instrument). The problem is that the time of the loop is not constant. Can I use a very short time (100ms) as the cycle of the instrument of the time, but use a longer period in time loop collect data?

    I know that many instrument offers the same capabilities, so the issue is relevant to each of them.

    Thanks for any help

    You're not going to be accurate with Windows. The time between samples should be that you have programmed the instrument (i.e. the time between each value in the table 1 d) but the rate of the iteration of a while loop always will be the subject of a jig on a bone not real-time.

  • Problem running two parallel while loops

    Hello world

    I'm new to Labview and is actually my first attempt. I intend to acquire data from two rockers simultaneously through two different ports. When I run my program attached with execution has highlighted, the second loop gets higher priority. How to prevent this? Also, I'm getting error codes when running arrives at the stage where Visa read data are passed to sweep of string function. Please suggest corrections to correct these problems.

    PS: I have not yet plugged on devices, that's why the properties of connection for the two Ports are the same at the moment.

    Kind regards

    Avi0111


  • How to synchronize parallel while loops?


    This will do what you want?

  • global variable functional to read and write data from and to the parallel loops

    Hello!

    Here is the following situation: I have 3 parallel while loops. I have the fire at the same time. The first loop reads the data from GPIB instruments. Second readers PID powered analog output card (software waveform static timed, cc. Update 3 seconds interval) with DAQmx features. The third argument stores the data in the case of certain conditions to the PDM file.

    I create a functional global variable (FGV) with write and read options containing the measured data (30 double CC in cluster). So when I get a new reading of the GPIB loop, I put the new values in the FGV.

    In parallel loops, I read the FGV when necessary. I know that, I just create a race condition, because when one of the loops reads or writes data in the FGV, no other loops can access, while they hold their race until the loop of winner completed his reading or writing on it.

    In my case, it is not a problem of losing data measured, and also a few short drapes in some loops are okey. (data measured, including the temperature values, used in the loop of PID and the loop to save file, the system also has constants for a significant period, is not a problem if the PID loop reads sometimes on values previous to the FGV in case if he won the race)

    What is a "barbarian way" to make such a code? (later, I want to give a good GUI to my code, so probably I would have to use some sort of event management,...)

    If you recommend something more elegant, please give me some links where I can learn more.

    I started to read and learn to try to expand my little knowledge in LabView, but to me, it seems I can find examples really pro and documents (http://expressionflow.com/2007/10/01/labview-queued-state-machine-architecture/ , http://forums.ni.com/t5/LabVIEW/Community-Nugget-2009-03-13-An-Event-based-messageing-framework/m-p/... ) and really simple, but not in the "middle range". This forum and other sources of NEITHER are really good, but I want to swim in a huge "info-ocean", without guidance...

    I'm after course 1 Core and Core 2, do you know that some free educational material that is based on these? (to say something 'intermediary'...)

    Thank you very much!

    I would use queues instead of a FGV in this particular case.

    A driving force that would provide a signal saying that the data is ready, you can change your FGV readme...  And maybe have an array of clusters to hold values more waiting to be read, etc...  Things get complicated...

    A queue however will do nicely.  You may have an understanding of producer/consumer.  You will need to do maybe not this 3rd loop.  If install you a state machine, which has (among other States): wait for the data (that is where the queue is read), writing to a file, disk PID.

    Your state of inactivity would be the "waiting for data".

    The PID is dependent on the data?  Otherwise it must operate its own, and Yes, you may have a loop for it.  Should run at a different rate from the loop reading data, you may have a different queue or other means for transmitting data to this loop.

    Another tip would be to define the State of PID as the default state and check for new data at regular intervals, thus reducing to 2 loops (producer / consumer).  The new data would be shared on the wires using a shift register.

    There are many tricks.  However, I would not recommend using a basic FGV as your solution.  An Action Engine, would be okay if it includes a mechanism to flag what data has been read (ie index, etc) or once the data has been read, it is deleted from the AE. 

    There are many ways to implement a solution, you just have to pick the right one that will avoid loosing data.

  • How image rotation parallel loop for?

    Dear all,

    I try to use the parallel loop to rotate an image 180 times, but by the time the cost was the same as without the parallel use of loops.

    Someone knows the reason?

    The parallel for loop looks like as below.

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