[overture] Re: A++ : Finding non-zeros in an array

  • From: Bill Henshaw <henshaw@xxxxxxxx>
  • To: overture@xxxxxxxxxxxxx
  • Date: Tue, 21 Apr 2009 19:49:31 -0700

Hi Dominic,
  The fastest way is to do this would be to grap
the Array_Descriptor.Array_View_Pointer (see e.g. primer/pwave.C)
and index the array as a C array. This would also avoid
extra memory required by the solutions below.

...Bill

#DOMINIC DENVER JOHN CHANDAR# wrote:

Hi Slava,

 Thanks for the idea ! .. Ive implemented this and its perfect ..

Regards,
Dominic

-----Original Message-----
From: overture-bounce@xxxxxxxxxxxxx
[mailto:overture-bounce@xxxxxxxxxxxxx] On Behalf Of Viacheslav Merkin
Sent: Tuesday, April 21, 2009 8:16 PM
To: overture@xxxxxxxxxxxxx
Subject: [overture] Re: A++ : Finding non-zeros in an array

Hi Dominic,

You could probably do something like this:


where ( X != 0)
  {
    intArray mask = 1;
    RealArray Y=X
}

int N_nonzeros = sum(mask);
Y.reshape(N_nonzeros);



I don't remember the exact P++ usage for the sum() and the reshape()
functions, but something like this should work, I think.

Regards,
Slava





On Apr 21, 2009, at 7:25 AM, #DOMINIC DENVER JOHN CHANDAR# wrote:


Hi,
I have an array of the form X = { P , P, P , P, A, A, A, P, P , P, A , A, A} 

P : finite value exists
A : value is zero
I would like to create a new array called Y = { P,P,P....} which has all the non-zero entries. I will not know the number of non-zeros unless I look into the array.. Using a simple loop, I believe this can be achieved.. but for large amount of data, it takes time. What could be the simplest way of doing 


this using A++ ?

I tried something like :

where ( X != 0)
 {
   RealArray Y=X
}
The non zero entries are there.. but the dimension of array Y is obviously that of X.. with the remaining padded with zeros. Is there a
way to redimension this.. keeping in mind that we dont know the size of Y .. 

Thanks,
Dominic

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