Algorithms

10-Feb-07 7:40

Just check if the next number minus current equals 1 and append -. Then replace ---- with -. However, I always liked seeing 1, 3, 4, 6 as that and not 1, 3-4, 6.

division algorithm

david bagaturia7-Feb-07 22:35

david bagaturia

7-Feb-07 22:35

Hi all.

I write class to handel the big integer number problem, but my division algorithm is to weak. if I wont to divid 'a' into 'b' I must get the bite code of 'a','b' and divide this numebr by using this bite code. it take tol of time and this algoritm works on integer number only.I wont to solwe this two problem.

Can some one help me and give better algorithm or tel where I can find it.

Thanks for any help.

Luc Pattyn8-Feb-07 2:27

Luc Pattyn

8-Feb-07 2:27

Doing division efficiently is not very straightforward; there are many algorithms.

You could have a look at:
- some "big integer" articles on CodeProject
- the GNU multi-precision library [^]
- hundreds of books, e.g. The Art of Computer Programming, Volume 2, Seminumerical
Algorithms, by Donald Knuth.
- Google

I myself would be interested in a .NET wrapper for the GNU library, because I work in
.NET and the GNU library is very extensive.

Regards

Luc Pattyn

Dan Neely8-Feb-07 3:39

Dan Neely

8-Feb-07 3:39

Luc Pattyn wrote:
I myself would be interested in a .NET wrapper for the GNU library, because I work in
.NET and the GNU library is very extensive.

Is the library released under the GPL, or LGPL?

--
Rules of thumb should not be taken for the whole hand.

Luc Pattyn8-Feb-07 4:10

Luc Pattyn

8-Feb-07 4:10

I dont know, but I did include the link...

Luc Pattyn

Bassam Abdul-Baki8-Feb-07 7:55

8-Feb-07 7:55

Look into MIRACL.

"It is the mark of an educated mind to be able to entertain a thought without accepting it." - Aristotle

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Are Jay8-Feb-07 8:22

Are Jay

8-Feb-07 8:22

Class Diagram::LongMath<br />
Addition <br />
Add(sourceA As String, sourceB As String) As String<br />
Subtraction <br />
Subtract(sourceA As String, sourceB As String) As String<br />
Multiplication <br />
Multiply(sourceA As String, sourceB As String) As String<br />
Division<br />
Divide(divisor As String, dividend As String) As String

source[^]

I'm listening but I only speak GEEK.

Luc Pattyn8-Feb-07 10:09

Luc Pattyn

8-Feb-07 10:09

Hi AreJay,

I was aware of this package, but I didnt mention it since I am not convinced
string representations will lead to good performance.

Most "big integer" packages use arrays of ints or something similar, which
is more computer-friendly.

Regards,

Luc Pattyn

Are Jay9-Feb-07 6:37

Are Jay

9-Feb-07 6:37

Luc Pattyn,
Thanks for the information. When I wrote the class using a string was the only way it made since to me but now I'll convert it to an int array instead of a char array. I've been working on my C# and hope to re-write my Long Math class with C# so any performance tips would be greatly appreciated. Thanks again for the helpful advice.

I'm listening but I only speak GEEK.

david bagaturia8-Feb-07 18:14

david bagaturia

8-Feb-07 18:14

thanks all , it help me lot.
Now I have new idea's.

I have class thet works with "big integer" and with "finite field", I wish thet it works for float to and it wos faster.
if I made good class thet works with "big integer and folat", I will publish it.

matrix of positions

anassamar4-Feb-07 11:42

anassamar

4-Feb-07 11:42

Hi,
I want to know, how I can get matrix of positions of pixels of image in the coordinate system (x,y) in matlab?

thank you
soso

discrete mathematics

studentprogrammer3-Feb-07 15:19

studentprogrammer

3-Feb-07 15:19

Can anyone suggest some online resources from which to learn discrete math and computer applications. Using C++, as my choice and writing code to classify functions, input relations from sets and test functions, Confused | :confused:

Re: discrete mathematics

Roger Wright12-Feb-07 11:41

Roger Wright

12-Feb-07 11:41

I found this site[^] rather interesting...

"...a photo album is like Life, but flat and stuck to pages." - Shog⁹

Unsolved Problems

Bassam Abdul-Baki3-Feb-07 9:05

Control direction of rounding.

3-Feb-07 9:05

UnsolvedProblems.org[^]

Re: Unsolved Problems

Paul Conrad3-Feb-07 15:26

Paul Conrad

3-Feb-07 15:26

Dan Neely25-Jan-07 2:44

Dan Neely

25-Jan-07 2:44

I have to convert a floating point range into inverse units (Hz to uSec, and back) while assuring that any rounding causes the range to widen, not narrow. A simple X = 1000000/Y conversion could result in rounding in either direction, and short of adjusting Y by an empirically determined delta large enough to always force the rounding in the correct direction I'm unable to think of a good way to control the rounding.

--
Rules of thumb should not be taken for the whole hand.

Bassam Abdul-Baki25-Jan-07 4:42

25-Jan-07 4:42

Isn't a ceiling function what you want, round up, but not down?

"Oh, what a tangled web we weave, when first we practice to deceive." - Sir Walter Scott

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Dan Neely25-Jan-07 5:14

Dan Neely

25-Jan-07 5:14

Probably.

I'm using doubles and keeping at most 9SF, so it's doubtful that a single division will throw the bogobits into the part being kept.

--
Rules of thumb should not be taken for the whole hand.

Bassam Abdul-Baki25-Jan-07 5:39

25-Jan-07 5:39

Multiply by 1o to the number of digits you wish to keep, ceil it, then divide by the power of 10 again. See if this gives you what you want.

"Oh, what a tangled web we weave, when first we practice to deceive." - Sir Walter Scott

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