Post Reply 
[HP35s] Program for prime number (Wheel Sieve and Miller-Rabin)
02-13-2019, 05:26 PM (This post was last modified: 02-13-2019 07:23 PM by Albert Chan.)
Post: #11
RE: [HP35s] Hello and program for prime number
Just to show what is involved doing Primality SPRP Test.
Example, Prove X = 56789 is composite

X-1 = 56788 = 2^2 * 14197 = 2^s * d
→ s = 2
→ d = 14197 = 0b11,011,101,110,101

Check if X is an a-SPRP, for a=2:
Bits Mod X
1     2^1 ≡ 2
1     2^3 ≡ 2² * 2 ≡ 8
0     2^6 ≡ 8² ≡ 64
1     2^13 ≡ 64² * 2 ≡ 8192
1     2^27 ≡ 8192² * 2 ≡ 25321
1     2^55 ≡ 25321² * 2 ≡ 10462
0     2^110 ≡ 10462² ≡ 21041
1     2^221 ≡ 21041² * 2 ≡ 50063
1     2^443 ≡ 50063² * 2 ≡ 13275
1     2^887 ≡ 13275² * 2 ≡ 18716
0     2^1774 ≡ 18716² ≡ 14104
1     2^3549 ≡ 14104² * 2 ≡ 38687
0     2^7098 ≡ 38687² ≡ 9874
1     2^14197 ≡ 9874² * 2 ≡ 35115 → a^d ≠ ±1
0     2^28394 ≡ 35115² ≡ 3668 → a^(2^r*d) ≠ -1, r < s

-> 56789 is *not* 2-SPRP
-> 56789 is *guaranteed* composite

2-SPRP may still be composite, but much less likely. Furthur testing may required.

An issue is how to do the squaring and multiply without overflow.
It may require splitting the numbers, and do in steps.
Find all posts by this user
Quote this message in a reply
Post Reply 


Messages In This Thread
RE: [HP35s] Hello and program for prime number - Albert Chan - 02-13-2019 05:26 PM



User(s) browsing this thread: 2 Guest(s)