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#51 2014-11-03 06:48:40

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 108,743

Re: Sum of R primes?

We will talk about that some other time.

Back in the days of yore, there was a language called TRS-80 BASIC. Now the machine had no harddrive, a cassete for external storage and only 16k of ram!


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#52 2014-11-03 07:18:08

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,648
Website

Re: Sum of R primes?

Do you miss that time?


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#53 2014-11-03 07:19:29

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 108,743

Re: Sum of R primes?

No but it illustrates why your program is not working.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#54 2014-11-03 07:23:06

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,648
Website

Re: Sum of R primes?

The code is inefficient


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#55 2014-11-03 07:24:56

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 108,743

Re: Sum of R primes?

Each time you call a subroutine the program has to know what to do with the return at the end of it. Has to know where to go. Savvy?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#56 2014-11-03 14:00:57

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,648
Website

Re: Sum of R primes?

That is recorded in a place called call stack which might blow up


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#57 2014-11-03 20:34:43

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 108,743

Re: Sum of R primes?

Each call pushes 4 bytes to the top of the stack. That means memory goes down by 4 bytes. You want to make 100's of millions of calls.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#58 2014-11-03 20:49:29

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,648
Website

Re: Sum of R primes?

Let us assume that the Goldbach Conjecture is true


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#59 2014-11-03 20:54:47

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 108,743

Re: Sum of R primes?

Has nothing to do with it.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#60 2014-11-03 20:55:28

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,648
Website

Re: Sum of R primes?

Which has nothing to do with it?


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#61 2014-11-03 20:59:34

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 108,743

Re: Sum of R primes?

The Goldbach conjecture.

Expressible[748776611396, 68906072498] makes 68906072497 calls to a subroutine. Each one is pushed onto the stack for storage. That is roughly 4 x 68906072497 bytes! Something has got to explode.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#62 2014-11-03 21:13:19

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,648
Website

Re: Sum of R primes?

Anyway, let us assume that the Goldbach conjecture is true


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#63 2014-11-03 21:15:50

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 108,743

Re: Sum of R primes?

Okay, we assume it is true?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#64 2014-11-03 21:16:37

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,648
Website

Re: Sum of R primes?

I have not had a ginger biscuit for long


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#65 2014-11-03 21:20:38

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 108,743

Re: Sum of R primes?

Hmmm, ginger biscuits and Goldbach's. I never really saw the connection.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#66 2014-11-03 21:26:05

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,648
Website

Re: Sum of R primes?

I'll telll you.


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#67 2014-11-03 21:33:25

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 108,743

Re: Sum of R primes?

I will wait for that answer.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#68 2014-11-03 21:50:39

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,648
Website

Re: Sum of R primes?

What is a good way to check if a number is a sum of m even numbers all of which is greater than 2?


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#69 2014-11-03 21:53:43

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 108,743

Re: Sum of R primes?

By writing a program to do it.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#70 2014-11-03 22:06:04

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,648
Website

Re: Sum of R primes?

Suppose R is even. Now, N is expressible as a sum of R primes if it is expressible as a sum of R/2 even numbers each of which is greater than 2 To do this, we check if (N-2*R) is even and greater than 2.

If R is odd, we check if there is a suitable prime p such that N-p is expressible as a sum of R-1 primes.


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#71 2014-11-03 22:08:10

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 108,743

Re: Sum of R primes?

I am not following you. What are we trying to do?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#72 2014-11-03 22:10:26

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,648
Website

Re: Sum of R primes?

We want to check if N is a sum of R primes


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

Offline

#73 2014-11-03 22:13:41

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 108,743

Re: Sum of R primes?

And if R = 2?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#74 2014-11-03 22:16:37

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,648
Website

Re: Sum of R primes?

Agnishom wrote:

Let us assume that the Goldbach Conjecture is true


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

Offline

#75 2014-11-03 22:21:36

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 108,743

Re: Sum of R primes?

Suppose R is even. Now, N is expressible as a sum of R primes if it is expressible as a sum of R/2 even numbers each of which is greater than 2 To do this, we check if (N-2*R) is even and greater than 2.

How does it work if N = 10 and R = 5?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

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