mersenneforum.org (https://www.mersenneforum.org/index.php)
-   Homework Help (https://www.mersenneforum.org/forumdisplay.php?f=78)
-   -   math gcd problem need help (https://www.mersenneforum.org/showthread.php?t=22585)

 crack11 2017-09-17 06:35

math gcd problem need help

1 Attachment(s)
Dear all im new in this Greatest forum i have problem in mathematica i need calculate gcd from this string:
[code]Z1:=(7580104959982914123117804044806461820154572036369549529405552162648856956231245030405896783337631871321017085933334306430501343909365379890910193903441-(7601611438277968963930435339966375537762723788929138241505092335032216337024111944145650540579951639515460945444623092013993572866002842083492323809287290^17592186175489));
Z2:= (7580104959982914123117804044806461820154572036369549301773204651044654156328611994019678602790933052049997074737942147009504600337458372628655015658163-(5472021051232020294637156058031796107019454396525172260491306567922450488302345750910648307191204110931670031994886144725045972546892458995859985546716414^17592186175489));
Z3:= (7580104959982914050609440727680305970398447676033232174897745114621599628756001756455762578505630805317234747401759098214730033873908508468766892578356-(2716401471494295676405217606243925186946305783849093640906079739928627393562677984831598246598185728284424287135181309232467496805930321500988187816347957^17592186175489));
ToUpperCase[IntegerString[(GCD[Z1,Z2,Z3]),16]][/code]

 ewmayer 2017-09-18 06:50

Your problem is not 'in mathematica', your problem is that you are blindly attempting to get mathematica to do a computation without having thought through how large those exponentials you are inputting are. So tell us - and you don't need any fancy maths package for this, just some simple digit-counting and basic algebra - roughly how many decimal digits will your GCD inputs have once the exponentiations are done?

 crack11 2017-09-18 11:00

Dear sir,

without mathe matica how its possibel its 64bit gcd computation my laptop dell i7 with 8GB RAM...

 axn 2017-09-18 11:34

The problem is the size of the calculation. What you want to do is impossible

 a1call 2017-09-18 11:37

Those numbers are too large for the available memory. Why don't you try the GCD function without the exponents and then raise it to the power of the smallest exponent?

The GCD (8^a,6^b,18^c)= 2^( Smallest of a,b ,c)
You can do all that programmatically if you wish.

 crack11 2017-09-18 11:38

 VBCurtis 2017-09-18 14:22

You've been given help. You haven't answered any of the questions posed in the replies, nor shown any indication you comprehend what you're trying to do.

 VBCurtis 2017-09-18 14:24

[QUOTE=a1call;468024]
The GCD (8^a,6^b,18^c)= 2^( Smallest of a,b ,c)[/QUOTE]

Huh? If a = 1, b = 2, c = 2, I'm pretty sure the GCD is not 2^1.

 CRGreathouse 2017-09-18 15:22

[QUOTE=VBCurtis;468032]Huh? If a = 1, b = 2, c = 2, I'm pretty sure the GCD is not 2^1.[/QUOTE]

Right, it should have been min(3a, b, c). But the point remains that the gcd needs to be computed symbolically rather than by blindly expanding then taking the gcd.

 Dr Sardonicus 2017-09-18 15:48

Hmm. I'm not familiar with Mathematica syntax. The three integers all seem to be of the form

a - b^17592186175489.

The three values of a are

7580104959982914123117804044806461820154572036369549529405552162648856956231245030405896783337631871321017085933334306430501343909365379890910193903441

7580104959982914123117804044806461820154572036369549301773204651044654156328611994019678602790933052049997074737942147009504600337458372628655015658163

7580104959982914050609440727680305970398447676033232174897745114621599628756001756455762578505630805317234747401759098214730033873908508468766892578356

which have a suspiciously long block of MSD's in common.

Beyond that, I don't see anything particularly useful.

 a1call 2017-09-18 16:26

[QUOTE=VBCurtis;468032]Huh? If a = 1, b = 2, c = 2, I'm pretty sure the GCD is not 2^1.[/QUOTE]

Good point. I did not think of that.
Thank you.

All times are UTC. The time now is 15:44.