checking big digit number as prime

drmurat · 2020-05-13, 08:24

which one is hard . calculating big digit number or checking it . which methods ca be use for checkig numbers ?

MODERATOR NOTE: Thread moved from FermatSearch forum

Uncwilly · 2020-05-13, 13:40

Are you asking how hard it is to take 2^332,199,893-1 and expand it to its full decimal form vs checking it to see if it is prime?
The first is very fast. Faster than the old machines could display it. The second is slow.

If you have some complex formula to calculate the number vs checking it to see if it is prime, even that, calculating the number is faster than checking it (in almost every case).

paulunderwood · 2020-05-13, 14:29

Quote:

Originally Posted by Uncwilly

Are you asking how hard it is to take 2^332,199,893-1 and expand it to its full decimal form vs checking it to see if it is prime?
The first is very fast. Faster than the old machines could display it. The second is slow.

If you have some complex formula to calculate the number vs checking it to see if it is prime, even that, calculating the number is faster than checking it (in almost every case).

Just to expand on your "in almost very case". PRP'ing a huge partitions number is quicker than computing its decimal digits (with the latest Pari/GP version). Proving it prime or even checking the certificate is a few orders more time-consuming.

VBCurtis · 2020-05-13, 17:25

As for "which methods" from the OP question- it depends on the form that describes your number, as well as how big "big digits" is.

Give us more info about what size and what form you have in mind, you'll get a better answer.

drmurat · 2020-05-13, 17:49

I think I am at the begining . :) I get 2^50.000 at first night with my own code . can we think it is big :) . I am recording all results from 2 ^ 1 to 2 ^ 50000 . and it goes on I want to calculate fermat and mersenne primes

paulunderwood · 2020-05-13, 18:03

Quote:

Originally Posted by drmurat

I think I am at the begining . :) I get 2^50.000 at first night with my own code . can we think it is big :) . I am recording all results from 2 ^ 1 to 2 ^ 50000 . and it goes on I want to calculate fermat and mersenne primes

If you taking about how long it takes to wrtie the number to file: The following takes ~1 ms with Pari/GP:

Code:

gettime();write("delMe",2^50000+1);gettime()
1

drmurat · 2020-05-13, 18:15

I am calculating 2^50000 and writing to file and calcupating 2^50001 and ... goes on . I get 2^60000 . big numbers get years and years ...

Uncwilly · 2020-05-13, 18:20

Apfloat also works nice: http://www.apfloat.org/apfloat/
Also http://numcalc.com/ handles it quickly
And 2^50000-1 is not prime. The exponent has to be prime.

drmurat · 2020-05-13, 18:29

thank you . it will be so helpfull to me . I get 2 ^ 65000

Uncwilly · 2020-05-13, 18:36

Quote:

Originally Posted by drmurat

thank you . it will be so helpfull to me . I get 2 ^ 65000

What are your plans (please use a paragraph to state it)? If you are just practicing your coding, look at places that can help you learn. If you don't trust what everyone else has done, you have issues. Are you testing the numbers using L-L? Or are you doing it via a more rudimentary way? What language/platform are you using? Why do you want the decimal expansion?

drmurat · 2020-05-13, 18:48

okay . I am not plannig to improve my coding . I am behind so many thing about primes . I am medical doctor . I know a bit coding . and intrested in with primes nearly 20 mounths .I do my calculations with my own . it has to reason fitst when I need data fot one process . getting whole data is hard . you must open so many zip files . make them as you want . it gets so time . the second reason making calculation with your own gives you a chance of oservation . I am asking here to calculating 2 ^70000 is hard . I realy dont know the answer .

2020-05-13, 08:24	#1
drmurat "murat" May 2020 turkey 2³·3² Posts	checking big digit number as prime which one is hard . calculating big digit number or checking it . which methods ca be use for checkig numbers ? MODERATOR NOTE: Thread moved from FermatSearch forum Last fiddled with by Dr Sardonicus on 2020-05-13 at 13:17 Reason: Note that thread was moved

2020-05-13, 17:49	#5
drmurat "murat" May 2020 turkey 48₁₆ Posts	I think I am at the begining . :) I get 2^50.000 at first night with my own code . can we think it is big :) . I am recording all results from 2 ^ 1 to 2 ^ 50000 . and it goes on I want to calculate fermat and mersenne primes Last fiddled with by drmurat on 2020-05-13 at 17:55

2020-05-13, 18:20	#8
Uncwilly 6809 > 6502 """"""""""""""""""" Aug 2003 101×103 Posts 23·401 Posts	Apfloat also works nice: http://www.apfloat.org/apfloat/ Also http://numcalc.com/ handles it quickly And 2^50000-1 is not prime. The exponent has to be prime. Last fiddled with by Uncwilly on 2020-05-13 at 18:21

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2020-05-13, 13:40	#2
Uncwilly 6809 > 6502 """"""""""""""""""" Aug 2003 101×103 Posts 23·401 Posts	Are you asking how hard it is to take 2^332,199,893-1 and expand it to its full decimal form vs checking it to see if it is prime? The first is very fast. Faster than the old machines could display it. The second is slow. If you have some complex formula to calculate the number vs checking it to see if it is prime, even that, calculating the number is faster than checking it (in almost every case).

2020-05-13, 17:25	#4
VBCurtis "Curtis" Feb 2005 Riverside, CA 2×5×463 Posts	As for "which methods" from the OP question- it depends on the form that describes your number, as well as how big "big digits" is. Give us more info about what size and what form you have in mind, you'll get a better answer.

2020-05-13, 18:15	#7
drmurat "murat" May 2020 turkey 110₈ Posts	I am calculating 2^50000 and writing to file and calcupating 2^50001 and ... goes on . I get 2^60000 . big numbers get years and years ...

2020-05-13, 18:29	#9
drmurat "murat" May 2020 turkey 2³×3² Posts	thank you . it will be so helpfull to me . I get 2 ^ 65000

2020-05-13, 18:48	#11
drmurat "murat" May 2020 turkey 2³·3² Posts	okay . I am not plannig to improve my coding . I am behind so many thing about primes . I am medical doctor . I know a bit coding . and intrested in with primes nearly 20 mounths .I do my calculations with my own . it has to reason fitst when I need data fot one process . getting whole data is hard . you must open so many zip files . make them as you want . it gets so time . the second reason making calculation with your own gives you a chance of oservation . I am asking here to calculating 2 ^70000 is hard . I realy dont know the answer .