The 3x + 1 class record search

 •  What software do I need to join?
 •  What's the impact on my system?
 •  How do I get a block assigned?
 •  How do I stop the search?
 •  How do I restart the search?
 •  How do results get reported?
 •  What if I want to abandon the project?
 •  What's the 3x+1 problem about, really?
 •  Frequently asked questions.
 •  What is the current progress?
Trajectory of 63,728,127

What software do I need to join?

You don't need anything special really. The main program is a small EXE program that can run on any Windows platform. So you need a PC. Sorry, there is no version for MacIntosh or Unix systems.
If you're not sure which one to run take the top one.

64-bits .NET Version (requires framework 4.0) download
64-bits .NET Version (requires framework 2.0/3.5) download
16-bits Version (requires Windows XP or earlier) download

What's the impact on my system?

The impact on your system is usually very low indeed:

On normal Windows versions the impact is almost nothing. The program runs on idle priority, so it just uses the cycles your machine would otherwise spend doing nothing. It writes just a single line of text to the hard disk every cycle - a cycle takes around 10 minutes on a 2GHz machine, it might take longer or shorter on your machine depending on the speed of your processor. It does not open any other files or use any other resources. It also does not send any emails or perform any other network activities.

Searches are performed in 'blocks' of 100,000,000,000,000 (100.1012). On modern PC's which often have multiple cores and can use hyperthreading such a block will take up to 12 days of (idle) time on a 2 GHz processor.

How do I get a block assigned?

The distributed search is done by assigning 'blocks' of 100.1012 numbers. Simply email and I'll reply to you with the next free block as soon as possible. You should then soon see your name appear on the progress page as well.
Then you start up the program - fill in the blocknumber(s) and blocklength(s) and press 'Start'.

How do I stop the search?

Simply press the 'Stop' buttons or quit the program. You quit the program by selecting it from the system tray and right-clicking it. Select 'Close' to close the program. Note that clicking on the 'normal' windows close button will only minimize the program to the system tray.

How do I restart the search?

When you restart the program it will pick up the blocks at the point it left off, but it will not automatically restart. You can start the program with the "/auto" flag, which will start all processes automatically and also minimize it straight to the system tray.

How do results get reported?

The program writes a log file entry every 18,000,000,000 numbers (which is 234), and also whenever it starts or finishes. It also logs every interesting number. There are not many interesting numbers at these big numbers, just about one in every 5 . 1012 , and sometimes they come in groups as well, so it is not at all strange if you search for a week and find (almost) nothing. The program also writes the time and the number of overflows found. This last number enables a check on whether results are correct and reproducible.

The idea is that once the block is finished you mail the logfile to . Logfiles are rather small (~230 kb), and of course you could zip them to make them even smaller.

What if I want to abandon the project?

Obviously you can always end your participation whenever you want to. Please tell me if you want to leave, that way I can ask someone else to finish your block. If you mail me the (perhaps incomplete) logfiles that saves work, too.
Occasionally it unfortunately happens that someone asks for a block but never finishes it. If a block is not finished after 5 months I will try to contact you. If I don't receive any reply I must assume you no longer wish to participate and I will have to reassign the block.

What's the 3x+1 problem about, really?

The 3x+1 problem is one of the simplest unsolved mathematical problems. You can read all about it at my 3x+1 homepage. A short and straightforward explanation can also be found at Wolfram's brilliant MathWorld website. If you're really interested try following the link to the Lagarias 3x+1 overview.

Frequently Asked Questions

Q:I inspected the logfile and saw it reported lots of overflows. Should this worry me?
A: Not at all. The program usually calculates in 64 bits. Occasionally a number is found that needs more than 64 bits to perform the calculation. Calculation for that number is then restarted using 128 bits. Every time this happens this is counted as an overflow. The number of overflows per 16 billion interval is reported to provide a check on the proper running of the program.
Q:How do I run the 16-bits version?
A: The older 16-bit version, written mostly in assembly, will run on Windows XP or anything earlier. This program comes with a small scriptfile to make it easier to restart the process after a system shutdown. This is written in VBScript.

If you would like to run this older version please contact me.

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