Rank: 5418 based on 1 downloads (last 30 days) and 1 file submitted
photo

Valentin Kuklin

E-mail

Personal Profile:
Professional Interests:

 

Watch this Author's files

 

Files Posted by Valentin
  • 1 - 1 of
  • 1
Updated   File Tags Downloads
(last 30 days) 		Comments Rating
09 Dec 2008 fastsearch Search an element in the array, or the next smaller and greater Author: Valentin Kuklin search, fastsearch, array, approximation, interpolation, element 1 8
  • 4.5
4.5 | 2 ratings
Comments and Ratings on Valentin's Files View all
  • 1 - 5 of
  • 8
Updated File Comment by Comments Rating
10 Nov 2008 fastsearch Search an element in the array, or the next smaller and greater Author: Valentin Kuklin Franworth, Dru

I tried the following code in Matlab

clear all

x=randn(10000,1);

tic
for i=1:1000000
y=randn;
g=find(abs(x-y)==min(abs(x-y)));
end
toc
tic
y=sort(x);
for i=1:1000000
z=randn;
qq=fastsearch(y,z,1);
end
toc
----------------------------------------------------------------------------------

This is the output:
Elapsed time is 423.486252 seconds.
Elapsed time is 357.878006 seconds.

-----------------------------------------------------------------------------------
An improvement by 15%. Pretty impressive.

10 Nov 2008 fastsearch Search an element in the array, or the next smaller and greater Author: Valentin Kuklin Franworth, Dru

There is a slight bug in your code. In line 134 , you should have
index=fastsearch_indeed(array,von,m1-1,wert,bias);

Instead, you have fastsearch(array,von,m1-1,wert,bias);

Same thing for line 136. Basically, all you have to do is replace fastsearch in lines 134 and 136 with fastsearch_indeed.

09 Nov 2008 fastsearch Search an element in the array, or the next smaller and greater Author: Valentin Kuklin Franworth, Dru

I tried the following code and got an error message. As you can see, the number I am searching for is inside the sorted vector but it is generating an error message.

-----------------------------------------------------------------------------------

>> x=randn(10000,1);
>> y=sort(x);
>> z=randn;
>> fastsearch(y,z,1)
??? Error using ==> fastsearch
Too many input arguments.

Error in ==> fastsearch>fastsearch_indeed at 137
        index=fastsearch(array,m2+1,bis,wert,bias);

Error in ==> fastsearch at 59
index = fastsearch_indeed(array,1,length(array),wert,bias);

>> z

z =

    0.4291

>> min(y)

ans =

   -3.5758

>> max(y)

ans =

    4.0050

>> find(abs(y-z)==min(abs(y-z)))

ans =

        6694
06 May 2008 fastsearch Search an element in the array, or the next smaller and greater Author: Valentin Kuklin Kuklin, Valentin

Hi Alexander,

thanks for your notes.

I think there is no bug. This code with "Check if wert is inside of array." is used only for the first run, for example if you have array=1:1:100 and you search -5 or 105. For the further runs it does not play any role, the searched number will be anyway within [von, bis]. Actually it can not be infinite recursion because every "if" ends with "return" but not with the new call of function.

But anyway I am happy that someone uses my function and tries to find bugs :) Thanks again :)

Valentin Kuklin
05 May 2008 fastsearch Search an element in the array, or the next smaller and greater Author: Valentin Kuklin Chemeris, Alexander

It's good that such a useful algorithm in finally implemented in Matlab :)
But this implementation have a bug. "Check if wert is inside of array." should looks like:

if wert<array(von)
    if bias==1
        index=von;
        return;
    else
        index=-1;
        return;
    end
end
if wert>array(bis)
    if bias == -1
        index = bis;
        return;
    else
        index = -1;
        return;
    end
end

That is "von" and "bis" are used instead of "1" and "end". Without this fix algorthm may enter infinite recursion in certain cases.
Top Tags Applied by Valentin
  • 1 - 5 of
  • 9
approximation, array, element, equal, fastsearch
Files Tagged by Valentin
  • 1 - 1 of
  • 1
Updated   File Tags Downloads
(last 30 days) 		Comments Rating
09 Dec 2008 fastsearch Search an element in the array, or the next smaller and greater Author: Valentin Kuklin search, fastsearch, array, approximation, interpolation, element 1 8
  • 4.5
4.5 | 2 ratings

Contact us at files@mathworks.com