Zero iteration for loop

Hi folks,
There's an old behavior that I'm pretty used to, but it still occasionally bites me (usually with references). It happened again today, and it got me to wondering if it's really intended behavior.
If you pass a value into a zero iteration for loop, then send it out the other side, the value exiting the for loop is returned to default, not the value you fed in (see simple.vi, LV7.1).
Any ideas?
Joe Z.
Attachments:
simple.vi ‏11 KB

This is expected behavior...the workaround is to use shift registers to pass the value through instead of tunnels. I believe this is discussed in the LabVIEW Help.
-D
Darren Nattinger, CLA
LabVIEW Artisan and Nugget Penman

Similar Messages

How to use no of iteration of for loop as the input for the for loop

hi all,
i wanna need some help here..
i'm using for loop to iterate to ceratin no of iteration.. then, i would like to use back the no of iteration as the input of 'N' for the next iteration..
in other word, eg:
1st run:
i insert a control to 'N', let say 80
then the iteration run until 80-1 = 79..
2nd run:
i need to insert the no of "N", let say a control of 120.. i want the loop run for "120 - 79", where the 79 is the no of previous run..
easy to say,
how can i connect the "i' as a control to ''N''
n how to make a "run' or ' GO' and ''stop'' button in the front panel and block diagram after the first run without using the stop and run from the labview window
thanks..

Jim
You're entirely bonkers. But I'll tell you a secret. All the best people are. ~ Alice
Attachments:
Untitled 2.vi ‏9 KB

A tunneled Excel refnum goes from a valid value to a NULL between iterations of a For Loop?

How would a tunneled Excel refnum go from a valid value to a NULL between iterations of a For Loop?
For
some reason this works find in one VI and when executed and not in
another. Here's screen shots of the highlighted execution with probes
appropriately. The "Open" refnum is passed into "Performance Test -
Write Data To Files.vi". That's where the trouble is. You can see
that it goes into the For Loop. The first iteration is okay, but the
second and subsequent iterations have the refnum NULL. See images
below.
(I don't know how to delete an accidental double post, sorry)
Message Edited by James DiLiberto on 01-22-2008 01:48 PM
Attachments:
Second Iteration1.jpg ‏158 KB
First Iteration1.jpg ‏145 KB
Second Iteration Error Dialog1.jpg ‏20 KB

Is there any chance that the Insert Data Into Excel VI is closing the reference or that it is closed anywhere else (e.g. through a local or by having its owner destroyed)?
I wouldn't expect the numeric value of the reference to change to 0, but since ActiveX is an external resource, I suppose that it's possible that the probe shows the number only if the resource is actually accessible.
Try to take over the world!

For loop vs Iterator

I'm writing an application in which performance will be quite important and was looking into my collection classes. I recently saw the move towards using Iterator instead of for loops, while loops to retrieve objects from a List. I wanted to test to see which performed better and I saw that for about 1,000,000 Integer objects, an Iterator was 100ms slower in time in both Vector and ArrayList than a for loop using gets.
1) Is the main cost the creation of the Iterator object?
2) If I'm not worried about manipulation of my List while I'm retrieving objects and I will always be using a List in which I can always pull indexes (instead of say using HashSet)... is there any reason to use Iterator instead of a for loop?
-- I read the recent tech tip on this and was just wondering if anyone had any other ideas of why to choose Iterator over for/while loops.
Thanks.

The purpose of Iterator
The purpose of the Iterator pattern is to handle the traversal of a collection of objects.
The advantages of Iterator has over other straightforward ways
The direct access methods provided by some collection classes may not be as efficient or simple as using iterator pattern. And because the iterator keeps its own state, multiple traversals can be performed on a single collection simultaneously.
An iterator hides the internal representation of the collection from the classes that need to access the contents of these collections.
An Iterator pattern provides a consistent and sometimes efficient way to access the objects or values in some collections.
What problems can arise if collection is changing?
While using iterator, the changes of a collection such as that adding new elements or deleting old elements can result in inconsistency of the data, for example some objects may be missed or accessed more than once.
How can they be avoided?
A simple way is to make a copy of the collection and work on this copy but this can be very costly in terms of memory and time.
Design a method that notifies the iterator whenever the collection is changed, and as soon as the change happens the iterator class throws an exception or restart whichever appropriate.
A better way would be implements methods that monitor the changes and adjust the iterator and the results so they are consistent to the contents of the collection at any time.
There are no general solutions to this problem and under different circumstance the proper solutions vary, however it is a good practice to taking possible changes of the source collections into account while designing the iterator, and it may be worth to let the user aware of the occurrence of any changes.

The speed of the "for loop iteration"

Hi all:
I have written a short mini program just to test out the speed of a "for loop iteration"
package generator;
* Title: 
* Description: 
* Copyright: Copyright (c) 2004
* Company: 
* @author not attributable
* @version 1.0
private static long tmp = 0;
public static int count=0;
public synchronized long getValue(){
 long value = 0;
 value = 10 * System.currentTimeMillis();
 if(value == tmp){
 value++;
 count++;
 tmp = value;
 return value;
public static void main(String[] args) {
 for (int i=0;i<1000;i++){
 getValue();
 System.out.println("count is " + count);
}And i find that on average, count will be a value between 498-500, which probably means that on average the speed of a for loop is around 0.5 ms. But I guess the speed of the "for loop " iteration is also very much CPU dependent, could somebody possibly give me some education on this issue :) ?
Also, anybody know exactly how System.currentTimeMillis works? For example, how does it get the current time from the OS, etc. let me know.
Again, Many many thanks...

Hi all:
I have written a short mini program just to test out the speed of a "for loop iteration"You will find the overhead of the getValue() call, the increments and most importantly the System.currentTimeMillis() is what you are timing.
 public static void main(String args[]) {
 int ITER = 1000000000;
 long start = System.currentTimeMillis();
 for(int i=0;i<ITER;i++);
 long end = System.currentTimeMillis();
 System.out.println("Iterations per sec="+ITER*1000L/(end - start));
 }Prints the following Iterations per sec=576368876Running on a 1.8 GHz Intel/Windows2000

LabVIEW 6.1 If For Loop count terminal is zero then value going through the loop is not passed on to the output of the loop

Hello, one of our customers just encountered an execution error in a vi running under LabVIEW 6.1, which doesn't exist under LabVIEW 5.1 or 6.01. I have a simple vi that has two encapsulated For Loops. Two string arrays go in, one goes out of the outer loop. Inside the outer loop the first array is indexed. The string which results from this indexing is compared with all other strings from the second string array in the inner loop. If it matches one of the strings of the second array, it is not outputted, otherwise this string goes through the inner For Loop to the output of the inner loop and from there to the output of the outer loop. The count
terminal of the outer/inner loop is connected to the Array Size of the first/second string array. If the second array is empty, that means that the element in test from the first arry cannot match anything from the second array, so the element in test is send to the output of the inner loop and from there to the output of the outer loop. This works fine in LabVIEW 5.1 and 6.01, but NOT in LabVIEW 6.1. In LabVIEW 6.1 the inner loop is never executed if the count value is zero (which is correct), but the data line running through the loop is not executed either, which is different to what LabVIEW 5.1 and 6.01 do. There, the input string is sent to the output of the inner loop correctly even if the loop counter is zero. The solution is easy - I just have to connect the output of the outer loop to the data line BEFORE it enters the inner loop. But: I don't know if this is a LabVIEW 6.1 bug or if it is supposed to be a feature, but it brings some incompatibility in programming between the
different LabVIEW versions.
Best regards,
Gabsi

Hi,
When a for-loop runs zero times, all outputs are 'undefined' (and should
be).
Besides, how would LV know what the output of a not executed routine should
be?
It might be handled differently in LV5 and LV6, which is unfortunate. In
both cases, the result is undefined.
It's not a bug. It's just something that should be avoided in any LV
version.
> The solution is easy - I just have to connect the
> output of the outer loop to the data line BEFORE it enters the inner
> loop. But: I don't know if this is a LabVIEW 6.1 bug or if it is
In some cases this does the trick. But if the data is changed in the inner
loop, this will effect the results if the N is not zero.
Technically, I think the output in this construction is also 'undefined'.
But LV handles this as expected / desired.
Another solution is to use a shift register. If N is zero, the input is
directly passed through to the output.
Regards,
Wiebe.
"Gabs" wrote in message
news:[email protected]...
> LabVIEW 6.1 If For Loop count terminal is zero then value going
> through the loop is not passed on to the output of the loop
>
> Hello, one of our customers just encountered an execution error in a
> vi running under LabVIEW 6.1, which doesn't exist under LabVIEW 5.1 or
> 6.01. I have a simple vi that has two encapsulated For Loops. Two
> string arrays go in, one goes out of the outer loop. Inside the outer
> loop the first array is indexed. The string which results from this
> indexing is compared with all other strings from the second string
> array in the inner loop. If it matches one of the strings of the
> second array, it is not outputted, otherwise this string goes through
> the inner For Loop to the output of the inner loop and from there to
> the output of the outer loop. The count terminal of the outer/inner
> loop is connected to the Array Size of the first/second string array.
> If the second array is empty, that means that the element in test from
> the first arry cannot match anything from the second array, so the
> element in test is send to the output of the inner loop and from there
> to the output of the outer loop. This works fine in LabVIEW 5.1 and
> 6.01, but NOT in LabVIEW 6.1. In LabVIEW 6.1 the inner loop is never
> executed if the count value is zero (which is correct), but the data
> line running through the loop is not executed either, which is
> different to what LabVIEW 5.1 and 6.01 do. There, the input string is
> sent to the output of the inner loop correctly even if the loop
> counter is zero. The solution is easy - I just have to connect the
> output of the outer loop to the data line BEFORE it enters the inner
> loop. But: I don't know if this is a LabVIEW 6.1 bug or if it is
> supposed to be a feature, but it brings some incompatibility in
> programming between the different LabVIEW versions.
> Best regards,
> Gabsi

Handle Error in for Loop and finish the iteration

I am using a for Loop now i encounter an error.
i want to handle this error but after that carry on with iteration of the loop.
Any Parallel to "Continue" in JAVA or any other solution for this...
Please Suggest.

You can use pl/sql block with exception inside the loop
Re: Continue beyond expcetion in proc...
Message was edited by:
jeneesh

Reasons why to use Iterator for List rather than for loop ?

when i use the iterator and for loop for traversing through the list. it takes the same time for iterator and also for for loop. even if there is a change it is a minor millisecond difference.
what is the actual difference and what is happening behind the traversing list through iterator
if we are using we are importing extra classes ...if we are using for loop there is no need to import any classes

If you have an array-backed collection, like an ArrayList, then the difference between using an iterator and get() will be negligible.
However, if you have a linked list, using get() is O(n^2) whereas iterator is O(n).
So with an iterator, regardless of what your underlying data structure, a list of 100,000 elements takes 1,000 times as long to iterate over as a list with 100 elements. But using get() on a LinkedList, that same 100,000 element list will take 1,000,000 times as long as the 100 item list.
There's no real benefit to ever using get()
Side note: I've been comparing iterators to get(), not iterators to for loops. This is because whether it's a for or a while has nothing to do with whether you use an iterator or get(). The way I use iterators is for (Iterator iter = list.iterator(); iter.hasNext(); ) {
Foo foo = (Foo)iter.next();
}

How to save a chart after each iteration in a for loop?

Hello,
I have written code which initializes a spectrometer. Once initialized, if the "Capture" button is pushed, the spectrometer takes a new spectrum three times (see for loop) every second. This spectrum is displayed as a chart in my front panel. My code runs fine...it will update the spectrum every second.
However, I want to be able to save each of these three iterations as separate graphs. Basically, I want to click "Capture" and have my code save three charts to a specified folder. How do I go about doing this?
I've attached my VI.
Thanks.
Solved!
Go to Solution.
Attachments:
Spectrometer Iteration.vi ‏444 KB

Use Build Array to make a 2D Array of your X and Y data and use Write To Spreadsheet File to save the data.
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How to output data outtside a for loop every 10 iterations?

Hi friends,
does any body help me to sort out this problem?
please check the attchement for my vi.
all i want is output data from inside for loop to outside for loop every 10 iterations. please do not use local variable.
Many thanks
dan
Attachments:
output.vi ‏16 KB

Hi Dan,
I am not sure what you want to do every 10 iterations with the value outside, but If you want to update your graph every 10 iterations use the following way:
If you want to handle the specific value every x iterations outside the loop you could either use queues or notifieres.
BR,
ThSa
Message Edited by ThSa on 08-23-2006 09:05 PM
http://www.newgistics.com
Attachments:
1.png ‏6 KB

Repeating nodes using FOR loop but when concating XML string then concating only last iteration of FOr loop ??

I stuck with a problem that I am using FOR loop for generating repeating nodes.
Now when I concat the generated node in the main node then I got only last iteration of that FOR loop.
can anybody suggest me a way to handle this error....
FOR i IN 1..pl_phone_tab.Count
LOOP
SELECT xmlelement("Phone"
 ,xmlelement("PHONETYPE",xmlattributes('01' AS "dmnADRP_PHONETYPE"),pl_phone_tab(i).p_phtype_tab)
 ,xmlelement("PHONENUM",pl_phone_tab(i).p_phnum_tab)
 ,xmlelement("PRIMARY_CONTACT",pl_phone_tab(i).p_prcon_tab)
INTO p_phone_xml
FROM dual; END LOOP;
SELECT xmlelement("PhoneInfo"
 ,xmlconcat(p_phone_xml))
INTO p_phone_info_xml
FROM dual;
here I am getting only one node but there has to be two nodes for PHONE node

Not that I'm encouraging you but here are two standalone examples explaining how to do what you want :
1) Loop through the input collection and append each node to its target container :
SQL> declare
2
3 type t_emp_tab is table of scott.emp%rowtype;
4
5 emp_tab t_emp_tab;
6 emp_info_xml xmltype;
7 emp_xml xmltype;
8
9 begin
10
11 -- filling emp_tab with data
12 select e.*
13 bulk collect into emp_tab
14 from scott.emp e
15 where e.deptno = 10;
16
17 emp_info_xml := xmltype('<EmpInfo/>');
18
19 -- looping through emp collection and appending to EmpInfo element
20 for i in 1 .. emp_tab.count loop
21 select appendchildxml(
22 emp_info_xml
23 , '/*'
24 , xmlelement("Emp"
25 , xmlattributes(emp_tab(i).empno as "id")
26 , xmlforest(
27 emp_tab(i).ename as "Name"
28 , emp_tab(i).job as "Job"
29 )
30 )
31 )
32 into emp_info_xml
33 from dual;
34 end loop;
35
36 dbms_output.put_line(emp_info_xml.getclobval(1,2));
37
38 end;
39 /
<EmpInfo>
<Emp id="7782">
 <Name>CLARK</Name>
 <Job>MANAGER</Job>
</Emp>
<Emp id="7839">
 <Name>KING</Name>
 <Job>PRESIDENT</Job>
</Emp>
<Emp id="7934">
 <Name>MILLER</Name>
 <Job>CLERK</Job>
</Emp>
</EmpInfo>
PL/SQL procedure successfully completed
2) Build a secondary collection of XML nodes and use XMLAgg to aggregate them in one go :
SQL> declare
2
3 type t_emp_tab is table of scott.emp%rowtype;
4
5 emp_tab t_emp_tab;
6 emp_info_xml xmltype;
7 emp_xml_tab xmlsequencetype := xmlsequencetype();
8
9 begin
10
11 -- filling emp_tab with data
12 select e.*
13 bulk collect into emp_tab
14 from scott.emp e
15 where e.deptno = 10;
16
17 -- looping through emp collection and appending to the collection of Emp nodes
18 for i in 1 .. emp_tab.count loop
19
20 emp_xml_tab.extend;
21
22 select xmlelement("Emp"
23 , xmlattributes(emp_tab(i).empno as "id")
24 , xmlforest(
25 emp_tab(i).ename as "Name"
26 , emp_tab(i).job as "Job"
27 )
28 )
29 into emp_xml_tab(i)
30 from dual;
31
32 end loop;
33
34 select xmlelement("EmpInfo", xmlagg(t.column_value))
35 into emp_info_xml
36 from table(emp_xml_tab) t ;
37
38 dbms_output.put_line(emp_info_xml.getclobval(1,2));
39
40 end;
41 /
<EmpInfo>
<Emp id="7782">
 <Name>CLARK</Name>
 <Job>MANAGER</Job>
</Emp>
<Emp id="7839">
 <Name>KING</Name>
 <Job>PRESIDENT</Job>
</Emp>
<Emp id="7934">
 <Name>MILLER</Name>
 <Job>CLERK</Job>
</Emp>
</EmpInfo>
PL/SQL procedure successfully completed
Both solutions give the same output.
Test them both and see which one fits better into your scenario.

ORA-24333: zero iteration count Cause: An iteration count of zero was specified for the statement Action: Specify the number of times this statement must be executed

Get the following error from Oracle
ORA-24333: zero iteration count
Cause: An iteration count of zero was specified for the statement
Action: Specify the number of times this statement must be executed
Any suggestions on whether is this a Oracle bug or if not what should be set to avoid this failure.

Hello get this from executing the following.
Occurs intermitently.
select MAX(LENGTH(lxVal)) from lxString_74501fb6 where lxType=910231053
Find the MaxLenght(LxVal) returned is null for this query.
Did google it but says the iterator not initialized. But not the case here
Thanks

For-loop & iterator.remove()

Is it possible to remove an item during iterating with for-loop?
for (SelectionKey opKey : selector.selectedKeys())
// I need to remove opKey from selectedKeys set.
}Is it really necessary to remove handled key from selectedKeys set? What will happen if I run selector.select() while selectedKeys set contains some keys?

Desiderata wrote:
Is it possible to remove an item during iterating with enhanced-for-loop?No
Is it really necessary to remove handled key from selectedKeys set? What will happen if I run selector.select() while selectedKeys set contains some keys?[Selector Selection|http://java.sun.com/j2se/1.5.0/docs/api/java/nio/channels/Selector.html#selop]

For loop 1 iteration execution time

Hi,
what is the time taken of for loop 1 iteration without code inside.How to calculate this Execution time.

Ravindranath.K wrote:
Hi,
what is the time taken of for loop 1 iteration without code inside.How to calculate this Execution time.
No code in the FOR loop? It will not use any time because the compiler will optimize it out.
Why do you even need to know?
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How to insert elements into an array after each iteration of a for loop

I am new to labview and working on an application where I am supposed to store an element into an array (without overwriting) after each iteration in a for loop. I have tried using Build Array Function keeping the indicator outside the for loop and played with indexing but didn't work. Please suggest me an idea how to do it.
Thanks
Solved!
Go to Solution.

Thank you for your suggestion.Here is my actual application attached . In the first image, a difference in time is evaluated and an enum const of insert into array is passed to the shift register where it takes to Insert element into array phase (Second image). I need to enter the time difference into an array after every loop iteration. Please have a look and could you let me know where I am mislead.
Attachments:
Image 1.JPG ‏88 KB
Image 2.JPG ‏71 KB

Zero iteration for loop

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