help cgsolve
  cgsolve : Solve a linear system A*x=b by conjugate gradients
 
  [x, niters, relres] = cgsolve(n, @Atimes, @getb);
 
  This routine solves the linear system A*x=b for x.
  The matrix A is not given explicitly, but rather as a
  user-supplied function that multiplies A by a given vector.
  The right-hand side b is given by a user-supplied function
  that returns individual elements of b.
 
  Inputs:
    n          integer: dimension of the matrix and vectors
    Atimes     function: y = Atimes(z,n) should return A*z
    getb       function: bi = getb(i,n) should return b(i)
  Outputs:
    x          vector: computed solution to A*x=b
    niters     integer: number of CG iterations performed
    relres     double: relative residual norm, defined as
                       norm(b-A*x)/norm(b)
 
  The CG algorithm requires the matrix to be symmetric and
  positive definite, though we do not check this.  We iterate
  either until the relative residual is less than 10^-6
  or for at most max(1000,10*sqrt(n)) iterations.  A more
  robust code would let the user specify the stopping condition.
 
  This is a sequential Matlab template -- CS240A homework 2 is 
  to implement this in parallel, including an "Atimes" routine
  that applies the 5-point model problem to a vector in parallel
  without ever actually forming the matrix.  In the parallel
  code, the vectors b, x, r, and d will all be distributed across 
  processors, and all the operations on vectors will be done by 
  calls to subroutines you write using MPI.
 
  John R. Gilbert     3 April 2011

[x,niters,relres] = cgsolve(9,@Atimes,@getb)
{??? Undefined function or method 'sqrt' for input arguments of type 'function_handle'.

Error in ==> <a href="matlab: opentoline('/Users/gilbert/Documents/CS240aWinter2014/Assignments/hw2/matlab/cgsolve.m',39,0)">cgsolve at 39</a>
maxiters = max(1000,5*sqrt(n));
} 
edit cgsolve
[x,niters,relres] = cgsolve(@Atimes,@getb,n)
{??? Undefined function or variable 'n'.
} 
[x,niters,relres] = cgsolve(@Atimes,@getb,9)
{??? Undefined function or method 'getb' for input arguments of type 'double'.

Error in ==> <a href="matlab: opentoline('/Users/gilbert/Documents/CS240aWinter2014/Assignments/hw2/matlab/cgsolve.m',42,0)">cgsolve at 42</a>
    b(i) = getb(i,n);
} 
whos
  Name       Size            Bytes  Class    Attributes

  dfile      1x21               42  char               

waht
{??? Undefined function or variable 'waht'.
} 
what

M-files in the current directory /Users/gilbert/Documents/CS240aWinter2014/Assignments/hw2/matlab

blockdiags     cgtest         modelmatvec    
cgsolve        grid5          startup        

help cgtest
  cgtest : Test cgsolve on the model problem
 
  cgtest(k)  creates a random right-hand-side b with k^2
             elements, then runs "cgsolve" to solve A*x=b
             where A is the 5-point model problem.

cgtest(3)
niters =
     5
relres =
   6.9804e-18
edit cgtest
cgtest(3)
xcg =
    0.5082
    0.4598
    0.5123
    0.6080
    0.6612
    0.6189
    0.3056
    0.4726
    0.5018
niters =
     5
relres =
   6.8310e-17
cgtest(3)
xcg =
    0.4852
    0.5876
    0.4016
    0.0219
    0.5200
    0.5720
    0.4157
    0.4641
    0.4551
niters =
     1
relres =
    0.7256
what

M-files in the current directory /Users/gilbert/Documents/CS240aWinter2014/Assignments/hw2/matlab

blockdiags     cgtest         modelmatvec    
cgsolve        grid5          startup        

edit modelmatvec
which getb
'getb' not found.
which getb
'getb' not found.
cgtest(3)
xcg =
    0.6196
    1.2391
    1.8587
    2.4783
    3.0978
    3.7174
    4.3370
    4.9565
    5.5761
niters =
     1
relres =
    0.5158
cgtest(3)
b =
    0.6948
    0.3171
    0.9502
    0.0344
    0.4387
    0.3816
    0.7655
    0.7952
    0.1869
xcg =
    0.6196
    1.2391
    1.8587
    2.4783
    3.0978
    3.7174
    4.3370
    4.9565
    5.5761
niters =
     1
relres =
    0.5158
cgtest(3)
b =
     1
     2
     3
     4
     5
     6
     7
     8
     9
xcg =
    0.6196
    1.2391
    1.8587
    2.4783
    3.0978
    3.7174
    4.3370
    4.9565
    5.5761
niters =
     1
relres =
    0.5158
clc
what

M-files in the current directory /Users/gilbert/Documents/CS240aWinter2014/Assignments/hw2/matlab

blockdiags     cgtest         modelmatvec    
cgsolve        grid5          startup        

edit cgtest
what

M-files in the current directory /Users/gilbert/Documents/CS240aWinter2014/Assignments/hw2/matlab

blockdiags     cgtest         modelmatvec    
cgsolve        grid5          startup        

ls
blockdiags.m		cgtest.m~		modelmatvec.m
cgsolve.m		diary-21-Jan-2014.txt	readme.text
cgtest.m		grid5.m			startup.m

edit modelmatvec
exit