The 3x + 1 class record search

Note
As of mid-2020 the project has switched to running NVidia/GPU based software only. This is simply a matter of speed. GPU-based software runs 20 to 50 times faster then CPU-based software. Therefore it is just not efficient anymore to run the CPU version for a week when the same work can be done on a GPU in around 6 hours.

 •  What software and hardware 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?
 •  What is the current progress? 		Trajectory of 63,728,127

What software and hardware do I need to join?

Since the project has switched to GPU-based software you will have to have an NVidia GeForce compatible card. It is not always obvious whether a GPU is compatible, but you can try to run the software if you want to. It should either run fine or terminate with an error within in a minute. Also you will have to run the software on any Windows platform. So you need a PC. Sorry, there is no version for MacIntosh or Unix systems.

64-bit .NET GPU Version 6.3 (Windows 7 or higher)
(the latest version (nov 2022) can handle input numbers up to 84 bits) 		download
64-bit .NET CPU Version 6.0.2 (Windows 7, 8 and 10)
(available for historical reasons only - no longer maintained) 		download

What's the impact on my system?

The impact on your system is mostly just an impact on your GPU:

The program tries to use the GPU as much as possible - therefore the load on the GPU can be quite high. If you feel this is a problem simply run the program for a few hours per day only.

Searches are performed in 'blocks' of 1,000,000,000,000,000 (1015). One such block takes 6-8 hours on a fast card to perhaps 20-24 hours on a slower one. So even if you run the program for a few hours per day you can still complete a fairly large interval during a week.

How do I get an interval assigned?

The distributed search is done by assigning a number of 'blocks' of 1015 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.
You start up the WonGPU program - fill in the path (just once), blockstart and blocklength and run the program. The real program will then start (in a text window) - its progress is reported. Also note that clicking on the 'normal' windows close button will minimize the management program to the system tray.

How do I stop the search?

Restore the program from the tray and simply press the 'Stop' button . This will quit the main program 'neatly' after at most (approximately) one minute. Note that nothing 'bad' happens if your pc crashes or if you kill the program. Next time it will restart from the last line in the log file.

How do I restart the search?

Start up the management program and restart the process. It will pick up the block at the point it left off.

How do results get reported?

The program writes a log file entry every 240 (~1012) numbers 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 1014 only, and sometimes they come in groups as well, so it is not at all strange if you search for a few days 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 not very large (around 60 kb per interval of 1e15), 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 3 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.

Back to the general 3x+1 page.