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Submitted on: 11/7/2009 8:42:25 AM
By: kaveh_aph
Level: Advanced
User Rating:
By 1 Users
Compatibility:VB 3.0, VB 4.0 (16-bit), VB 4.0 (32-bit), VB 5.0, VB 6.0
Users have accessed this code 1012 times.
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| | | Very Fast Prime Numbers Generator.
for me find primes-->
1 to 100,000 in 0.230 seconds.
1 to 1,000,000 in 4.5 seconds.
1 to 10,000,000 in 96.3 seconds.
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Other 1 submission(s) by this author
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 Report Bad Submission | | | | | Your Vote! | |
See Voting Log | | | | Other User Comments |  11/4/2009 1:01:40 PM: Salar Zeynali
Khoobe ! :D
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| 11/5/2009 4:03:10 AM: AOTChronoTrigger
This is more "intermediate" than "advanced" code, and has a few bad practices which should be addressed...:
First and foremost, you're not saving but a couple of CPU cycles by hard-coding in primes lower than 13. You might as well start at 3 and save some lines of code.
Second, for best performance, you really don't want to have a DoEvents inside of your realtime loop. The system **will** interrupt the process and write the buffer to disk when the write buffer is too full, and since you're not doing any informational visual updates until after all is done, you really don't need it.
CONT'D==>>
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| 11/5/2009 4:04:04 AM: AOTChronoTrigger
<<==CONT'D
Third, if you're using DoEvents for window responsiveness and/or pausing/stopping the execution, you could just divide up the number you're calculating up to by some number, and on each group of calculations do an update. That is, slicing, say, 113731 into 170 pieces (roughly sqr(113731) / 2, which can be calculated once) and doing an update every time it's gone through 1/170 of the numbers. Yes, that method grows with the input, but you could just as easily do a mindless 113731 / 32 and slice it into 32 pieces of work to do (at a cost of about 1778 items per update, versus about 670.) My point being, using a DoEvents with a pseudo-random number is wasting a large number of cycles that could be used to do real work, and any semi-modern (5 - 10 years old) computer will process that many numbers with exceptional speed. Worst-case, you're better off doing IF ((P& AND 371) < 3) THEN DOEVENTS instead of invoking the pseudo-random number generator. :-)
CONT'D==>>
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| 11/5/2009 4:04:20 AM: AOTChronoTrigger
<<==CONT'D
Fourth, you're allocating 80MB of memory for your prime number list (PR), as soon as the program starts. Allocating fixed-size arrays is generally bad practice -- do it dynamically, so you're 1) not wasting memory, and 2) can accommodate for more than 10,000,000 primes (prime number 10,000,000 = 179,424,673 by the way -- far below the 100,000,000th which can be calculated with the data types you're using -- 2,038,074,743... a VB Long can accommodate -2,147,483,648 to +2,147,483,647.)
Fifth, the internal VB listbox control has serious limitations on both the number of items you can add, as well as the size of each item. If you're going to rely on VB to present this information, you should use two listboxes -- one representing a set of results in a given range (or number of elements), and another with specific results in a given range (or number of elements.) For example, a first listbox containing "2 - 65536", "65537 - 131072", etc.
CONT'D==>>
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| 11/5/2009 4:04:35 AM: AOTChronoTrigger
<<==CONT'D
Sixth, your pause and stop buttons don't work the way they should, ideally; you should save your calculation state and stop calculation altogether until the pause button is clicked again (preferred method.) Otherwise all you do is introduce a race and tight loop into the execution, which only further ties up the processor core, rather than freeing it to perform other work. And neither the stop nor pause buttons interrupt the statistic calculations (which should be entirely optional with a checkbox, by the way.)
And last, stay away from the common dialog control! It's outdated and is very easily replaced by a few common dialog API calls. With a few exceptions, even intermediate code should stay away from the VB-supplied custom controls.
CONT'D==>>
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| 11/5/2009 4:09:09 AM: AOTChronoTrigger
<<==CONT'D
Oh, and I forgot to mention that the listboxes at the bottom cover each other if you click two that are next to each other. They need more space between them.
Those suggestions aside, this works, but I couldn't recommend it for fast prime calculation, as there are other submissions which use prime number sieves to calculate much larger primes in much less time. Still, for a straightforward implementation, this contains at least two improvements over brute-testing each number...
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| 11/5/2009 5:27:44 AM: AOTChronoTrigger
Sorry, in my last post I posted that you're being limited to -2^31 to +2^31-1 for your primes, but you're actually using doubles, which have much higher ranges. But, the implementation of floating-point numbers is much slower than integers in most cases, so this code is still taking a performance hit for that.
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