Another Prime!

Today I found a prime number!
9155 · 2^1311239 + 1 is prime, and is 394 727 digits long. It enters the database as the 2036 largest prime known to date.

In my efforts to meet my goal for posting 6 articles this year, I will write about idle computing. PrimeGrid, which I used to find the prime, uses the idle computing time on your CPU to look for the next largest prime.

My original interests in idle computing started with the World Community Grid back in March 2012. One of my friends introduced it to me, pointing out that most computers around the world are never used to their full capacity. World Community Grid (WCG) harvests that idle computing power in search for more effective treatments for cancer, HIV/AIDS and neglected tropical diseases. The way it works is that research teams around the world submit their project to WCG, and WCG distributes bits and pieces of the project to volunteer hosts around the world. Each host is given a piece of the puzzle to work on, called a work unit. Most of the time these work units take anywhere between 10 minutes to 10 days to complete. When the host completes a work unit, the host will announce it to WCG and returns the result and is issued a new work unit. You may wonder: How can you trust that it is good work? Well, initially WCG actually issues two copies of the work to it’s users and compares the results obtained. Once the host passes the test; that is, it returns results that are properly computed, then it is moved into the trusted section and less verification is required. It will still randomly check certain work units for accuracy; and also to compare it against new hosts joining the grid.

My reason for starting WCG was because my computer was on for the vast majority of the day already, mining bitcoins with my GPU. Hence I figured that I should but my CPU to use also. It is important to note that while it making use of idle computing power, running WCG will increase the power consumption, and generate a lot of heat. Living in Canada, the generated heat is welcomed during the winter months; and using power to compute problems while generating heat is a better idea then simply using an electric heater to heat the house. Usually I scale down or stop computing over the summer months as it is too hot to be generating extra heat!

I stayed loyal to WCG for over a year; donating over 5 CPU-years towards various projects that I deemed worthy, such as AIDS and malaria, which each got 1 a little over a year of computation. Note that the computation time is calculated per CPU – hence a quad core can provide 4 CPU years in a regular year if left on all year. In early 2013, the project pool diminished significantly, as most projects were completed in late 2012. I could not justify computing for the other available projects, so I started my search for other projects worthy of my CPU time. I tried different projects until I discovered PrimeGrid. Since then, I have mostly redirected my computing power towards finding new prime numbers. After breaking for summer, I found my first prime in December 2013, and the second one in March 2014. Today marks the day which I found my third prime number!


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