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Odd Behavior of DIALOG DOEVENTS with PB 8.03

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  • Odd Behavior of DIALOG DOEVENTS with PB 8.03

    I have a program that sits in memory checking for the continuous presence of another program which must be running and which has setup its Mutex.

    The code below shows what this program does while doing nothing. It just executes a loop, counting down the time lapsed until it is time to check again. In order to minimize CPU use I use the DIALOG DOEVENTS statement.

    IF I compile this program with PB 7.04 it works nice. The CPU use as reported by the task administrator is 00. IF However I compile it using PB 8.04 the CPU use goes up to 99 in slow computers and somehow lower in faster computers. I haven´t installed PB 9.00 yet.

    Any suggestions?

    Code:
         VerifyAgain:
         ' Check for Mutex
         lpClassName = $MUTEX_SEGURIDAD1
    
         lResult = App_PrevInstance(lpClassName)
    
         ' If the program we are checking is running, do nothing, wait, and check again.
         IF lResult <> 0 THEN  ' PROGRAM IS IN MEMORY
    
              OriginalmenteEnMemoria = 1
              ' Wait 5 minutes to check again
              InitialTime = TIMER
              DO
                   CurrentTime = TIMER
                   DIALOG DOEVENTS
                   IF CurrentTime - InitialTime > PermanentWait THEN
                        ' Once the wait time is up, check again
                        GOTO VerifyAgain
    
                   END IF
              LOOP
         END IF

  • #2
    From BOB ZALE
    "In PowerBASIC 8.04, the DIALOG DOEVENTS statement assumes an incorrect default value of zero (0) for the optional SLEEP& parameter. The correct default value should actually be one (1). This would cause execution to pause for 1 millisecond if there are no pending messages to process.

    We recommend that all existing code be changed to add an explicit SLEEP& value of one (1) to all DIALOG DOEVENTS statements in your programs.

    DIALOG DOEVENTS 1 -or-
    DIALOG DOEVENTS 1 TO count&

    This will allow your programs to compile and execute correctly with both current versions and future versions of PowerBASIC. The correct default value for this parameter will be used in the next release of this compiler."


    This was posted to the powerbase forum on Oct 21, 2007.
    KS



    Comment


    • #3
      Yes, that did it. I should have researched a little bit more before posting.
      Thanks Keith.

      Comment


      • #4
        No problem, when I can answer a question, I am happy to do it.
        KS

        Comment


        • #5
          ' Wait 5 minutes to check again
          SLEEP 5000 instead of checking every 1 millisecond?

          If there is a user interface here (code not shown), run this wait in a separate thread of execution...
          OR
          Use Waitable Timer Object Demo June 2005

          In either case, there is no longer any concern about DIALOG DOEVENTS defaults or CPU usage or any of that.


          MCM
          Michael Mattias
          Tal Systems (retired)
          Port Washington WI USA
          [email protected]
          http://www.talsystems.com

          Comment


          • #6
            Originally posted by Michael Mattias View Post
            SLEEP 5000 instead of checking every 1 millisecond?

            MCM
            You may have a point there but since I´ve read a lot about the deeds of SLEEP I rather use another method.

            No, the program does not have any dialogs or windows. I just stays in memory checking for the other program. It is a security program that takes action when it does not detect the other program in memory.

            By the way, SLEEP 5000 = 5 sec.
            SLEEP 30000 = 5 min.

            I may use DIALOG DOEVENTS 1000 or DIALOG DOEVENT 30000 instead. Whatever works best.

            Thanks for your input.

            Comment


            • #7
              > By the way, SLEEP 5000 = 5 sec.
              >SLEEP 30000 = 5 min.

              Whoa. I have simply GOT to start reading the "What's New" more carefully. (:doh

              BTW..
              > I´ve read a lot about the deeds of SLEEP I rather use another method

              ???

              AFAIK, SLEEP() is efficient. My point was more "why check every (less than five minutes)" if you are not going to do anything EXCEPT every five minutes?
              Michael Mattias
              Tal Systems (retired)
              Port Washington WI USA
              [email protected]
              http://www.talsystems.com

              Comment

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