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For..Next..For What?

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    For..Next..For What?

    For..Next.. seems like a good way to do repeating xbasic.

    It is not.

    Think about it:

    If you want alpha to jump a hundred times, you say:
    For i=1 to 100
    jump
    next i

    How does alpha handles this command?
    I do not know for sure, but one would assume that, at minimum alpha will have to:
    1-Create a counter starting with 1
    2-Jump once
    3-Increase the counter by one
    4-Check the counter against the end point of 100
    5-If the current counter is less than or equal to 100, alpha jumps else it quits.

    So, besides creating the counter, for every jump, there is the added:
    1-increasing the counter by one
    2-testing the counter against the end point
    These two extra steps will be done a 100 times.

    Is there a better alternative? I don't see why you can't write consecutive lines of xbasic
    jump
    jump
    jump
    ...
    etc.

    No, you do not have to type them 100 times. Go to Excel, type once, hold & drag to the 100's row, copy & paste to alpha.

    Now this might sound trivial, and most of the time it is. But if you are dealing with complex commands, a large loop or multiple loops it will make a difference. Test it and see.
    Last edited by G Gabriel; 12-08-2006, 03:14 PM.

    #2
    Re: For..Next..For What?

    Did you test it? I find the for...next loop to execute in 2/3 the time on a very simple test.

    Code:
    st = time("0h:0m:0s.3")
    for i = 1 to 3508
    	test_char = "nothing here"
    next
    nd = time("0h:0m:0s.3")
    ui_msg_box("Result"," "+(toseconds(nd)-toseconds(st))+ " seconds")
    end
    - .047 seconds

    vs

    Code:
    st = time("0h:0m:0s.3")
    test_char = "nothing here"
    test_char = "nothing here"
    test_char = "nothing here"
    test_char = "nothing here"
    test_char = "nothing here"
    'repeated 3508 total times
    test_char = "nothing here"
    nd = time("0h:0m:0s.3")
    ui_msg_box("Result"," "+(toseconds(nd)-toseconds(st))+ " seconds")
    end
    - .078 seconds

    And there seems to be a script count of lines limit somewhere around 4840 lines, depeiding on the total character count I imagine.
    There can be only one.

    Comment


      #3
      Re: For..Next..For What?

      Stan:
      Try this:
      Code:
      dim t as t=now()
      dim x as n=123456789123456789.123456789
      for i=1 to 2000
      	x=x*123456789123456789.123456789
      	next i
      	dim t1 as t=now()
      	ui_msg_box("time lapsed",str(t1-t,80,10))
      The alternative executes in half the time, 0.031 as opposed to 0.062.

      Comment


        #4
        Re: For..Next..For What?

        Originally posted by G Gabriel View Post
        Stan:
        Try this:
        Code:
        dim t as t=now()
        dim x as n=123456789123456789.123456789
        for i=1 to 2000
        	x=x*123456789123456789.123456789
        	next i
        	dim t1 as t=now()
        	ui_msg_box("time lapsed",str(t1-t,80,10))
        The alternative executes in half the time, 0.031 as opposed to 0.062.
        Not here.
        There can be only one.

        Comment


          #5
          Re: For..Next..For What?

          One would hope the designers optimize For ... Next performance by reading and storing the code block so that it could simply be run multiple times. Inline code (with repeating code blocks) would be much more difficult to optimize. In all likelihood the inline code must be interpreted line by line, instead of just being read once. -- tom

          Comment


            #6
            Re: For..Next..For What?

            Stan:
            You must have had them reversed. I am getting the opposite results.

            Comment


              #7
              Re: For..Next..For What?

              Originally posted by G Gabriel View Post
              Stan:
              You must have had them reversed. I am getting the opposite results.
              And exactly how do you suppose I took a screenshot of the message box over the just run code?
              There can be only one.

              Comment


                #8
                Re: For..Next..For What?

                And exactly how do you suppose I took a screenshot of the message box over the just run code?
                If you tried it in the IW, it only has 940 or so lines. You couldn't possibly write the 2000 lines. Tried within any form of yours.
                Correction:
                I was able to get more than 2000 lines in the IW. Therefore, don't have expalanation.
                Further correction:
                The IW seems to be limited by the number of characters not lines. So, back to the first comment.
                Last edited by G Gabriel; 12-08-2006, 04:44 PM.

                Comment


                  #9
                  Re: For..Next..For What?

                  What results for "x" are you gentlemen getting?

                  Comment


                    #10
                    Re: For..Next..For What?

                    What results for "x" are you gentlemen getting?
                    I don't even know if there is a word for it! It must be something equivalent to the US Treasury deficit.

                    Comment


                      #11
                      Re: For..Next..For What?

                      Originally posted by G Gabriel View Post
                      If you tried it in the IW, it only has 940 or so lines. You couldn't possibly write the 2000 lines. Tried within any form of yours.
                      Correction:
                      I was able to get more than 2000 lines in the IW. Therefore, don't have expalanation.
                      Further correction:
                      The IW seems to be limited by the number of characters not lines. So, back to the first comment.
                      Unfamiliar with the "IW", am I. The screen shot is of the script in edit mode from the code tab of the control panel.
                      There can be only one.

                      Comment


                        #12
                        Re: For..Next..For What?

                        G, shouldn't alpha be able to display it for you? This is best measure that the two approaches are running equivalent code... by comparing the numeric output from each. what I think you're going to find is that your sequence cannot be completed by Alpha Five because it exceeds allowable numeric size constraints. If Alpha can't compute the figure then I posit that the time comparisons are invalid. Should be comparing a loop that Alpha can complete. My 2 cents.

                        ?123456789123456789^2000
                        = 1.#INF
                        -- tom

                        Comment


                          #13
                          Re: For..Next..For What?

                          Tom:
                          You make a good point. I tried to find what x is to no avial. The number of zeros is googlish. Excel quits afte few calculations.

                          Nonethless, the same conditions occur in both tests. You could design any other test that would be time consuming in order to illustrate a meaningful difference, perhaps multiply by a certain number then in the following line divide by the same number so you wouldn't get in the realm of google. Maybe something like:
                          Code:
                          dim t as t=now()
                          dim x as n=123456789123456789.123456789
                          for i=1 to 2000
                          x=x*123456789123456789.123456789
                          x=x/123456789123456789.123456789
                          	next i
                          	dim t1 as t=now()
                          	ui_msg_box("time lapsed",str(t1-t,80,10))

                          Comment


                            #14
                            Re: For..Next..For What?

                            'for next' will always be faster because it was written in c
                            and will require one less step in the interpretation process
                            Cole Custom Programming - Terrell, Texas
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                            Comment


                              #15
                              Re: For..Next..For What?

                              Martin:
                              because it was written in c
                              I thought alpha never wrote anything in c !

                              Comment

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