error detects in labs in spmd

hi,

I have problem with this code , I can not know what is the reason.

this error what I got:

Starting matlabpool using the 'local' configuration ... connected to 2 labs. Lab 2:

ans =

       0

??? Error using ==> spmd_feval at 8 Error detected on lab(s) 2

Error in ==> test at 7 Nofusers=700;k1=1;

Caused by:

    You must call TIC without an output argument before calling TOC
    without an input argument.

    Error stack:
    (No remote error stack)

%%%the code%% clc;clear;close all;

N=2;    % Number of your CPU core, in my case, 4
matlabpool(N) % open N multicores for the parallel computation
tic
spmd    % similar with for loop 
  Nofusers=700;k1=1;

      f=fopen('d:\matlab\r2011a\bin\data_net.txt');
  for i=1:Nofusers
  gl=fgetl(f);
  celcod{i}=str2num(gl);
  end
  fclose all
  toc
  matlabpool close    % you must close the multicore calculation statement
   end

thanks

Answer 1

[Walter Roberson]

Your nesting appears to be off. You have the "matlabpool close" and the "toc" before it inside the spmd block.

Each lab is effectively a different MATLAB session. The "tic" before the spmd block is not in the same session as the "toc" inside the spmd block.

[huda nawaf]

thanks, the problem is not relate tic or toc, although I changed their position. when correct it as u indicated, Starting matlabpool using the 'local' configuration ... connected to 2 labs. I got: Lab 1:

ans =

       0

Lab 2:

ans =

       0

??? Error using ==> spmd_feval at 8 Error detected on lab(s) 2

Error in ==> test_parfor at 8 Nofusers=700;k1=1;

Caused by:

    Cannot execute    matlabpool close    on the labs.

    Error stack:
    matlabpool.m at 125

[huda nawaf]

Please I need example show me the difference in terms of time between code use spmd and other code do not use it

d=magic(100)%% array 100*100

B=inv(d); c=B^2;

Thanks in advance

[Walter Roberson]

Please show your revised code.

[huda nawaf]

hi Walter, thanks

My real code is more complex, but I try with simple code. I found the time of parallel is longer.that even if I used larger arrays and if code has more processing.

c(1:50,1:100)=4;
c1(1:50,1:100)=5;
celcod{1}=c;
celcod{2}=c1;
 c2=[c ;c1];

%%parallel code

   matlabpool(2)

tic

spmd

      for j=1:50
      for i=1:100
          s=0;
          for k=1:100
  f=celcod{labindex}(j,k)+c2(i,k);
  s=s+f;
          end
  ff{labindex}(j,i)=s;
      end
      end

end
toc
%ff{labindex}(1:6,1:12)
 matlabpool close
%%serial code
   tic
 for j=1:100
    for i=1:100
        s=0;
        for k=1:100
f2=c2(j,k)+c2(i,k);
s=s+f2;
        end

f3(j,i)=s;

      end

      end
  toc

[Walter Roberson]

Okay, so is there any question left at this point?

[huda nawaf]

The above process in serial take long time so I want use parallel , but when use it I found the serial is faster.

Why??

[huda nawaf]

walter look below, I took another example

clear, clc
  matlabpool open local 2
a=4000;b=2000;
  x{1}=rand(a);
      x{2}=rand(a);
      v=magic(a);
      y=rand(a*2);
      v1=magic(a*2);
       tic
  %%parallel code   
      spmd
          tic
          c=x{labindex}+ v;
          c1=x{labindex}.* v;
          c2=x{labindex}./v;

        toc;
        end

         toc
         matlabpool close
%%%serial code
         tic

            x1 = y+v1;
            x2=y.*v1;
            x3=y./v1;
             toc;

%%%% this result what I got

Starting matlabpool using the 'local' configuration ... connected to 2 labs.
Lab 1: 
  Elapsed time is 0.375403 seconds.
Lab 2: 
  Elapsed time is 0.306954 seconds.
Elapsed time is 6.215617 seconds.
Sending a stop signal to all the labs ... stopped.
Elapsed time is 0.955548 seconds.

%%%%

I used tic and toc regarding parallel before use spmd and aftr it.

Now I do not know which time I have to depend to know the time of parallel code

do sum the time of lab1 and lab2? or depend the time total time (6.215617)?

thanks

[Walter Roberson]

Depend on the total time (6.215617)

Your semantic error appears to be repaired.

Was your task to observe "the difference in terms of time between code use spmd and other code do not use it" ? If so then you have done that. Or was your task to come up with some code that runs faster using spmd than with serial? Because if your task was to explain the timings then you should be studying the documentation about how spmd works.

[huda nawaf]

In fact, the last example to know which time I have to depend and why serial faster than parallel. But my problem in first code is to know if I used spmd correctly. thanks