(11C) Prime or Not Prime Number

01202018, 01:04 PM
(This post was last modified: 01252018 09:33 AM by Gamo.)
Post: #1




(11C) Prime or Not Prime Number
This program check to see if the number is Prime or not Prime number.
Result 0 is Not Prime Number Result 1 is Prime Numer Code:
Here is another program to develop the Next Number of Prime. Code:
Example: if the start number is prime the same starting number repeated. Start 110 B > 113 > Repeat R/S > 127, 131, 137, 139,.... Start 13 B > 13 > Repeat R/S > 17, 19, 23, 29,..... Large number will compute faster with the modern 15C Try this number 899,880,277 to start. Repeat R/S for next prime is 899,880,281 in 2 second using HP15C Emulator on PC. Gamo 

01202018, 06:17 PM
(This post was last modified: 01202018 06:43 PM by Dieter.)
Post: #2




RE: (11C) Prime or Not Prime Number
(01202018 01:04 PM)Gamo Wrote: This program check to see if the number is Prime or not Prime number. Your program divides the input n by every divisor from int(sqrt(n)) down to 2. Why don't you simply use DSE then? Code: LBL A But this method is not very efficient as it also checks all even divisors. These could be sorted out. Also testing the divisors in ascending order usually is much faster. For numbers up to 1 000 000 you can use ISG which is faster than a manually controlled loop: Code: LBL A For n > 1 000 000 a manually controlled loop is required: Code: LBL A This version returns the smallest divisor of n. If this is 1, n is prime. ;) Example: 13573 f [A] => 7 n is divisible by 7 13577 f [A] => 1 n is prime Dieter 

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