Question

I have a for-loop which performs the following function:

Take a M by 8 matrix and:

1. Split it into blocks of size 512 elements (meaning X by 8 of the matrix == 512, and the number of elements can be 128,256,512,1024,2048)
2. Reshape the block into 1 by 512 (Number of elements) matrix.
3. Take the last 1/4 of the matrix and put it in front,
   e.g. Data = [Data(1,385:512),Data(1,1:384)];

The following is my code:

for i = 1 : NumOfBlock  
    if i == 1  
        Header = tempHeader(1:RowNeeded,:);  
        Header = reshape(Header,1,BlockSize); %BS  
        Header = [Header(1,385:512),Header(1,1:384)]; %CP  
        Data = tempData(1:RowNeeded,:);  
        Data = reshape(Data,1,BlockSize); %BS  
        Data = [Data(1,385:512),Data(1,1:384)]; %CP  
        start = RowNeeded + 1;  
        end1 = RowNeeded * 2;  
    else  
        temp = tempData(start:end1,:);  
        temp = reshape(temp,1,BlockSize); %BS  
        temp = [temp(1,385:512),temp(1,1:384)]; %CP  
        Data = [Data, temp];  
    end

    if i <= 127 & i > 1
        temp = tempHeader(start:end1,:);
        temp = reshape(temp,1,BlockSize); %BS
        temp = [temp(1,385:512),temp(1,1:384)]; %CP
        Header = [Header, temp];
    end

    start = end1 + 1;
    end1=end1 + RowNeeded;  
end

Running this loop with 5 million element will take more than 1 hour. I need it to be as fast as possible (in sec). Is this loop able to be vectorized?

Answer 1

Once again I would like to thanks Amro for giving me an idea on how to solve my question. Sorry for not making myself clear in the question.

Here is my solution to my problem:

%#BS CDMA, Block size 128,512,1024,2048  
  BlockSize = 512;  
  RowNeeded = BlockSize / 8;  
  TotalRows = size(tempData);  
  TotalRows = TotalRows(1,1);  
  NumOfBlock = TotalRows / RowNeeded;  
  CPSize = BlockSize / 4;  

%#spilt into blocks  
  Header = reshape(tempHeader',[RowNeeded,8, 128]);  
  Data = reshape(tempData',[RowNeeded,8, NumOfBlock]);  
  clear tempData tempHeader;  

%#block spread & cyclic prefix  
    K = zeros([1,BlockSize,128],'single');  
    L = zeros([1,BlockSize,NumOfBlock],'single');  
       for i = 1:NumOfBlock  
           if i <= 128  
              K(:,:,i) = reshape(Header(:,:,i),[1,BlockSize]);  
              K(:,:,i) = [K((CPSize*3)+1:BlockSize),K(1:CPSize*3)];
           end  
           L(:,:,i) = reshape(Data(:,:,i),[1,BlockSize]);  
           L(:,:,i) = [L((CPSize*3)+1:BlockSize),L(1:CPSize*3)];
        end