Here is the code snipet i need help with... for i = 1:end_frame for j = 1:1024 fout(i,j) = ifft(Z(i,j)); end end As you can see, if the end_frame is large, the for loop would take so long. What alternatives can I do? I've tried fout = ifft(Z); but it doesn't seem to give out the right answer. I've also tried for i = 1:end_frame fout(i,:) = ifft(Z(i,:)); end but again it gives a different answer. Which one gives the right answer anyway? And could you help me out becuase this part takes very long in my program. By the way, the dimension of Z is Z(1:end_frame,1:1024) 

Finding a Faster Way
Started by ●January 2, 2004
Reply by ●January 3, 200420040103
Hi, ifft(z) where z is a matrix gives inverse DFT of each column of the matrix. > for i = 1:end_frame > for j = 1:1024 > fout(i,j) = ifft(Z(i,j)); > end > end Here above, you are just taking one element of the matrix for computation of idft. I guess this is not what you wanted. and the other way you tried > for i = 1:end_frame > fout(i,:) = ifft(Z(i,:)); > end Here you are computing idft for each row of the matrix, so you get a different answer in all the three cases. Just check your input matrix and apply the appropriate method. regards, Ravi > Here is the code snipet i need help with... > > for i = 1:end_frame > for j = 1:1024 > fout(i,j) = ifft(Z(i,j)); > end > end > > As you can see, if the end_frame is large, the for loop would take > so long. What alternatives can I do? > > I've tried fout = ifft(Z); but it doesn't seem to give out the right > answer. > > I've also tried > for i = 1:end_frame > fout(i,:) = ifft(Z(i,:)); > end > but again it gives a different answer. > > Which one gives the right answer anyway? And could you help me out > becuase this part takes very long in my program. By the way, the > dimension of Z is Z(1:end_frame,1:1024) > V Ravi Chander 200211014 MTech (ICT) DAIICT ________________________________________________________________________ "If everything seems under control, you're just not going fast enough."  Mario Andretti ________________________________________________________________________ 
Reply by ●January 3, 200420040103
It seems there are end_frame no of frames and in each frame is of 1024 values, right? So, unless U take N pt IFFT (where N >24), U cant get correct answer. Try this  N = 1024; % or any higher value for m=1:end_frame fout(m,:) = ifft(Z(m,:), N); end So far as execution speed is concern, remember we are not implementing it on DSP kit. It's on simulation platform. so, it will be slower always. Regards Santosh ^.*.^.*.^.*.^.*.^.*.^.*.^.*.^.*.^.*.^.*.^.*.^.*.^.*.^.*.^.*.^.*.^.*.^.*. ^.*.^. , /) Santosh V Jadhav, // Narmada127, Finolex Housing Colony, (/ Zadgaon Block, Ratnagiri415639 _/ _______ ) ( (( Phone: (02352) 221559(R) /~~~\ \ SVJ \ (02352) 228361505(O), \___/ \ FAMT \ (022) 25764486 (TIDSP Lab, IITB) _)______) `` EMails: IITB Home page  http://www.ee.iitb.ac.in/uma/~santoshj IITB Official Page  http://www.ee.iitb.ac.in/Home/People/Students/PhD/info?02407802 _.*._.*._.*._.*._.*._.*._.*._.*._.*._.*._.*._.*._.*._.*._.*._.*._.*._.*. _.*._. > > Here is the code snipet i need help with... > > for i = 1:end_frame > for j = 1:1024 > fout(i,j) = ifft(Z(i,j)); > end > end > > As you can see, if the end_frame is large, the for loop would take > so long. What alternatives can I do? > > I've tried fout = ifft(Z); but it doesn't seem to give out the right > answer. > > I've also tried > for i = 1:end_frame > fout(i,:) = ifft(Z(i,:)); > end > but again it gives a different answer. > > Which one gives the right answer anyway? And could you help me out > becuase this part takes very long in my program. By the way, the > dimension of Z is Z(1:end_frame,1:1024) > > _____________________________________ > Note: If you do a simple "reply" with your email client, only > the author of this message will receive your answer. You need to do a > "reply all" if you want your answer to be distributed to the > entire group. > > _____________________________________ > About this discussion group: > > To Join: > > To Post: > > To Leave: > > Archives: http://www.yahoogroups.com/group/matlab > > More DSPRelated Groups: http://www.dsprelated.com/groups.php3 > Yahoo! Groups Links > > To > > 
Reply by ●January 5, 200420040105
hi, try both: 1. initialize the memory for fout before the for loop. eg: fout(1:1024,1:end_frame) = 0 or null ; 2. instead of calling ifft so many times, write ur self, a specialized ifft for ur length. go to ifft.m and copy only some lines into ur program.... regards, ravi ygamez <> wrote: Here is the code snipet i need help with... for i = 1:end_frame for j = 1:1024 fout(i,j) = ifft(Z(i,j)); end end As you can see, if the end_frame is large, the for loop would take so long. What alternatives can I do? I've tried fout = ifft(Z); but it doesn't seem to give out the right answer. I've also tried for i = 1:end_frame fout(i,:) = ifft(Z(i,:)); end but again it gives a different answer. Which one gives the right answer anyway? And could you help me out becuase this part takes very long in my program. By the way, the dimension of Z is Z(1:end_frame,1:1024) _____________________________________ Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer. You need to do a "reply all" if you want your answer to be distributed to the entire group. _____________________________________ About this discussion group: To Join: To Post: To Leave: Archives: http://www.yahoogroups.com/group/matlab More DSPRelated Groups: http://www.dsprelated.com/groups.php3  Yahoo! Groups Links To Yahoo! India Mobile: Ringtones, Wallpapers, Picture Messages and more.Download now. 