 
					
					
						Baillie-PSW Primality Test					
				 
				
					
						 المؤلف:  
						Baillie, R. and Wagstaff, S. W. Jr
						 المؤلف:  
						Baillie, R. and Wagstaff, S. W. Jr					
					
						 المصدر:  
						"Lucas Pseudoprimes." Math. Comput. 35, 1391-1417
						 المصدر:  
						"Lucas Pseudoprimes." Math. Comput. 35, 1391-1417					
					
						 الجزء والصفحة:  
						...
						 الجزء والصفحة:  
						...					
					
					
						 9-9-2020
						9-9-2020
					
					
						 977
						977					
				 
				
				
				
				
				
				
				
				
				
			 
			
			
				
				Baillie-PSW Primality Test
Baillie and Wagstaff (1980) and Pomerance et al. (1980, Pomerance 1984) proposed a test (or rather a related set of tests) based on a combination of strong pseudoprimes and Lucas pseudoprimes. There are a number of variants, one particular version of which is given by the following algorithm (Pomerance 1984):
1. Perform a base-2 strong pseudoprime test on  . If this test fails, declare
. If this test fails, declare  composite and halt. If this test success,
 composite and halt. If this test success,  is probably prime. Proceed to step 2.
 is probably prime. Proceed to step 2.
2. In the sequence 5,  , 9,
, 9,  , 13, ..., find the first number
, 13, ..., find the first number  for which the Jacobi symbol
 for which the Jacobi symbol  . Then perform a Lucas pseudoprime test with discriminant
. Then perform a Lucas pseudoprime test with discriminant  on
 on  . If this test fails, declare
. If this test fails, declare  composite. It if succeeds,
 composite. It if succeeds,  is very probably prime.
 is very probably prime.
Pomerance (1984) originally offered a prize of $30 for discovery of a composite number which passes this test, but the dollar amount of the offer was subsequently raised to $620 (Guy 1994, p. 28).
No examples of composite numbers passing the test are known, and as of June 13, 2009, Jeff Gilchrist has confirmed that there are no Baillie-PSW pseudoprimes up to  . However, the elliptic curve primality proving program PRIMO checks all intermediate probable primes with this test, and if any were composite, the certification would necessarily have failed. Based on the fact that this has not occurred in three years of usage, PRIMO author M. Martin estimates that there is no composite less than about
. However, the elliptic curve primality proving program PRIMO checks all intermediate probable primes with this test, and if any were composite, the certification would necessarily have failed. Based on the fact that this has not occurred in three years of usage, PRIMO author M. Martin estimates that there is no composite less than about  digits that can fool this test.
 digits that can fool this test.
REFERENCES:
Arnault, F. Ph.D. thesis, p. 72.
Baillie, R. and Wagstaff, S. W. Jr. "Lucas Pseudoprimes." Math. Comput. 35, 1391-1417, 1980. https://mpqs.free.fr/LucasPseudoprimes.pdf.
Gilchrist, J. "Pseudoprime Enumeration with Probabilistic Primality Tests (Fermat Base 2, Baillie-PSW)." https://gilchrist.ca/jeff/factoring/pseudoprimes.html.
Guy, R. K. "Pseudoprimes. Euler Pseudoprimes. Strong Pseudoprimes." §A12 in Unsolved Problems in Number Theory, 2nd ed. New York: Springer-Verlag, pp. 27-30, 1994.
Martin, M. "Re: Baillie-PSW - Which variant is correct?" https://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&selm=3FFF275C.2C6B5185%40ellipsa.no.sp.am.net.
Martin, M. "PRIMO--Primality Proving." https://www.ellipsa.net.
Nicely, T. R. "The Baillie-PSW Primality Test." https://www.trnicely.net/misc/bpsw.html.
Pomerance, C. "Are There Counterexamples to the Baillie-PSW Primality Test?" 1984. https://www.pseudoprime.com/dopo.pdf.
Pomerance, C.; Selfridge, J. L.; and Wagstaff, S. S. Jr. "The Pseudoprimes to  ." Math. Comput. 35, 1003-1026, 1980. https://mpqs.free.fr/ThePseudoprimesTo25e9.pdf.
." Math. Comput. 35, 1003-1026, 1980. https://mpqs.free.fr/ThePseudoprimesTo25e9.pdf.
				
				
					
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