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Speeding Up a Loop Inside a User Defined Function

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  • Speeding Up a Loop Inside a User Defined Function

    I created a UDF to test (random selection) a population of 5 million theoretical records. Although I have not attempted to run this sample against the full 5 million, I have tested it against 50,000 and 150,000 records and noticed that my function will process 50,000 records in 70 seconds and 150,000 in 275 seconds. The results or the records selected are captured in an array. I included the basic building blocks of my function in the code section below so you can get an idea on how I structured the UDF. My concern is that the speed of the function is slowing down as more records are processed. I also noticed that my CPU usage for Alpha stays around 8.5% and the memory usage stays around 70 mb. If there is a way to utilize the full capacity of my CPU, I am open to suggestions. If there is a more efficient method to design my UDF, I will appreciate any input. I did try to maximize the efficiency of my UDF through the following:

    • The function type is V
    • The function does not make any calls to any other global UDF
    • While minimizing the use of functions, any necessary functions are embedded in my UDF.
    • I minimized the use of variables unless necessary.


    Code:
    myFunction as V ()
    
    dim sample[] as P
    dim some_other_vars
    
    for i = 1 to 5000000[INDENT]ranNum = my_Embedded_RanNum_Generator()
    
    if ranNum < .01 then[/INDENT][INDENT=2]
    dim a as L[/INDENT][INDENT=2]a = meets_criteria_check()
    
    if a then[/INDENT][INDENT=3]sample[].number = i
    sample[..].other_stuff = other stuff[/INDENT][INDENT=2]end if[/INDENT][INDENT]end if[/INDENT]
    
    next i
    
    file.From_property("test/test.txt", sample)
    
    End Function
    I realize I could break out my criteria check into its own independent process to reduce the loops but the combined process time may be the same. I was hoping someone would have a suggestion on the function as is before I go down this road. Could changing the loop method make a difference? It appears Alpha is only using 1 of my 12 processing cores. Is there a way to increase this?
    Thanks,
    James

  • #2
    Re: Speeding Up a Loop Inside a User Defined Function

    What if you try this? Depending on what other variables you have defined, you might want to add it to the other embedded functions.

    Code:
    myFunction as V ([COLOR="#FF0000"]vars as p = local_variables()[/COLOR])
    [COLOR="#FF0000"]WITH vars[/COLOR]
    dim sample[] as P
    dim some_other_vars
    
    for i = 1 to 5000000
    ranNum = my_Embedded_RanNum_Generator()
    
    if ranNum < .01 then
    
    dim a as L
    a = meets_criteria_check()
    
    if a then
    sample[].number = i
    sample[..].other_stuff = other stuff
    end if
    end if
    
    next i
    
    file.From_property("test/test.txt", sample)
    [COLOR="#FF0000"]END WITH[/COLOR]
    End Function
    Robin

    Discernment is not needed in things that differ, but in those things that appear to be the same. - Miles Sanford

    Comment


    • #3
      Re: Speeding Up a Loop Inside a User Defined Function

      James,

      I don't see a need to declare (dim) the variable "a" each time through the loop. Consider moving it to the line before "for i = 1 ....."

      Then assign it the value FALSE at the top of the loop, before the ranNum var is populated.

      Two functions are called each time through the loop, neither are shown.
      my_embedded_ran_num_generator()
      meets_criteria_check()

      these should be examined for ways to be improved

      Comment


      • #4
        Re: Speeding Up a Loop Inside a User Defined Function

        Tom, good point but this only happens in the code I provided in the message. It does not exist in my actual function. I just did a piss poor example of my code. My original question should also probably be revised to: Why is their a degradation in speed within a for..next loop when you are adding information to a property array? It becomes apparent after 100,000 loops.

        I did find that my seed number (used in my embedded random number generation function) was being created every time I requested a random number which it should not be. Once the seed number is generated, it should not be changed. This will allow me to reproduce the sample as long as I record the original seed number. Changing this helped. Now I can process 150,000 records in 134 seconds instead of 275. 300,000 records takes 460 seconds so my degradation still exists as it takes 326 seconds to process an additional 150,000 records.

        I am setting up several other alternative methods to process this volume and will post back my results. The two other methods I will try are as follows:
        1. Record the results to a text file instead of a property array. I have a feeling the rapid growth in the property array size is causing the degradation but I am not sure. Recording the results to a text variable or directly into a text file may alleviate this issue. I can always pull it into an array from the final text that is generated.
        2. Create a master function that breaks up the loops into 100 sub-loops so that I can delete the property array before the start of each sub-loop. This will keep the array size from growing too large and should keep the speed of each sub-loop close to the results above. Right now I am just throwing s**t on the fan to see if it sticks.


        If anyone else has some suggestions or has come across a similar issue with for..next loops, please let me know. I will post my test results and final random number generator function in case anyone is interested.
        Thanks,
        James

        Comment


        • #5
          Re: Speeding Up a Loop Inside a User Defined Function

          Without doing any of the testing myself, it is possible that as you progress into a greater number of records being processed, your system is using virtual memory in
          addition to RAM.
          Have you considered a breakpoint (ex: append the data to a txt file every 75000 records), this would most likely keep you in ram and minimize the writes to disk.
          Gregg
          https://paiza.io is a great site to test and share sql code

          Comment


          • #6
            Re: Speeding Up a Loop Inside a User Defined Function

            I think Gregg has a good point.

            Have you told us how much memory is being allocated for each addition to the array? Have you compared the cumulative memory requirements with available RAM? Are other processes running in the background that consume memory resources?

            Comment


            • #7
              Re: Speeding Up a Loop Inside a User Defined Function

              Thanks for your input. I did consider the memory but there is no indication that this is causing the problem. When I run, the cumulative memory does not exceed 16% and Alpha is using approx 8.5% of the CPU and 70mb of my 32gb memory. Using msinfo32, I have available physical memory of 26.4gb and virtual of 28.4gb.

              I have an AMD processor with 6 cores (12 virtual). What I find interesting is the process only appears to be using 1 virtual core which is 8.33% of my capacity. Is it possible to force Alpha to use more of the available cores? I have tried using the Alpha function that selects the best processor but it did not make a difference.
              Thanks,
              James

              Comment


              • #8
                Re: Speeding Up a Loop Inside a User Defined Function

                I think I have it figured out. As far as I can tell, there is no issue with my code. The speed is what it is. I did do a speed test on the for i loop where I processed data using 4 different methods. Two of the methods displayed severe degradation and one method was the clear winner. I have attached the workspace that has the test function and my random number generator. Feel free to test against your system but the conclusion should not change. Although using a property array, like I did, may make sense at first, recording your data to a table or temporary table and converting it to an array later will speed up your large loops. Below are the test results. Also notice that recording your data to a file does not result in any degradation. Had my test looped 200,000 instead of 100,000, the file method would have come in second place in both speed and relative speed.

                For i Loop Speed on 100,000 Loops (in seconds)
                Increment To Property Array To Character Var To File To Table
                1
                6
                15
                53
                4
                2
                19
                73
                102
                8
                3
                38
                173
                151
                12
                4
                64
                312
                200
                16
                5
                97
                491
                249
                20
                6
                137
                713
                299
                24
                7
                184
                979
                352
                28
                8
                238
                1286
                401
                32
                9
                299
                1636
                450
                36
                10
                365
                2034
                499
                40
                Relative Speed (Indexed)
                Data to Table
                1
                Data to Array
                9.1
                Data to Text File
                12.5
                Data to Character Var
                50.9
                Attached Files
                Thanks,
                James

                Comment

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