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Options – Prime Numbers
This window is accessed via the menu item Options / Other and clicking on the
'Prime Numbers' tab.
This window can be used to specify the number of prime numbers known to UltimaCalc. The prime numbers are stored in a file. It is not possible to reduce the number of primes known below the quantity stored in the file, except by the rather drastic method of deleting the file. A minimum size file of 100,000 primes will be automatically rebuilt if the previous one is deleted or lost.
The work of building or extending this file occurs independently in the background and therefore UltimaCalc can be used as normal while this is done. A message box will pop up to tell you when this task has finished. NB: If a second incarnation of UltimaCalc is running, it should not be set to calculate more primes if the first one is doing this already, as the file would become corrupted.
To increase the number of primes required, click and hold down on the upper of the two arrows. The longer you hold the mouse button down on an arrow, the faster the count will change. When you let go of the mouse button, the rate of change will start off slowly again next time you click on an arrow. A note underneath will show you the size of the file that will be generated for the selected number of primes.
The maximum number of primes that can be computed is a little over two hundred million. These can take a few minutes to calculate and will result in a file of 138MB. Progress can be monitored by occasionally opening this window and looking at the number of primes known. It is recommended that you do not close UltimaCalc until it informs you that the task is complete.
After the file is created, only small parts of it are read into memory at any one time, so the amount of RAM required by prime numbers is quite small and is independent of the size of the file. The burden of using a file of 200 million primes lies entirely in the realm of hard disk capacity, and the time taken to calculate these primes in the first place.