Very slow loop execution

Question

Hello,
This subset of my program is running extremely slow.
There is a fair bit of computation involved with medium size data sets (1000 rows and 1500 columns) but this should not be the issue I think...
I am running a regression algorithm and I am cross validating the results using a single training data set...so basically you have a a data file (2D array) with my response and predictor variables and the algorithm takes the first row out builds the training model with the remaining data and predicts onto the row that was left out, then the first row is included back in the analysis and the algorithm moves onto the second row, it take it out and makes the training model with the remaining data and predicts onto the second row that was taken out...etc... (sorry if this is not explained clearly but it may not be so important) using the code shown in the attached image.
I get the feeling the slowness is due to my programming.
As you can see I am running 2 for loops, one inside another. The orange vi contains my model and the yellow vi contains the algorithm for predictions.
The outer loop subsets the number of data points to leave out of the analysis (i.e. it could be a single row or it could be any number of rows at a time) and the inner loop tells the program to run the regression algorithm up to a maximum number of runs.
I guess my questions are: (i) is there problems with programming with 2 for loops like I have done? and (ii) does my programming with 2 for loops look efficient? or is there a better way to do this?
I am sorry if this is not clearly explained. Please let me know if you want some more information.
Best wishes
RVR

Answer 1

RVR wrote:
Note that the vi's inside this orange sub vi are straight forward matrix computations - no loops inside.
At last attach your code images at full size. These scaled down version are pretty unreadable. From what I can tell, you're running in circles, doing a lot of unecessary operations. for example, inside the orange subVI, you delete a constant row from the array, but since the input is the same during all iterations of the inner loop, you're just doing repetitive work. a lot of code can be pulled outside the loop.
Then you are jumping through all these flaming hoops in the orange vI, constantly converting between 1d and 2d arrays without really adding any extra data. Look at the code segment on the picture. You are creating a 1d array of size N at the autoindexing output tunnel, then you convert it to a 1xN 2d array which you subsequently reshape to a 1d array of size N, giving you back what you had in the first place. Why????
 What is the purpose??
Message Edited by altenbach on 05-01-2007 01:25 AM
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Attachments:
whydoallthis.png ‏4 KB