conv_time=zeros(1,150);fft_time=zeros(1,150);
for L=1:150
   tc=0;tf=0;
   NI=2*L-1;nu=ceil(log10(NI)/log10(2));N=2^nu;
     for I=1:100
        h=randn(1,L);
        x=rand(1,L);
        t0=clock;
        y1=conv(h,x);
        t1=etime(clock,t0);   
        tc=tc+t1;
        t0=clock;
        y2=ifft(fft(h,N).*fft(x,N));t2=etime(clock,t0);
        tf=tf+t2;
        end
        conv_time(L)=tc/100;
        fft_time(L)=tf/100;
   end
n=1:150;subplot(1,1,1);
plot(n(25:150),conv_time(25:150),n(25:150),fft_time(25:150))