30 November 2025   8:49:19.653 AM
 
fem2d_poisson_cg()
  FORTRAN90 version:
  Solve the Poisson equation using sparse storage
  and a conjugate gradient solver.
 
  Solution of the Poisson equation in an arbitrary region
  in 2 dimensions.
 
  - DEL H(x,y) DEL U(x,y) + K(x,y) * U(x,y) = F(x,y) in the region
 
                    U(x,y) = G(x,y) on the boundary.
 
  The finite element method is used,
  with triangular elements,
  which must be a 3 node linear triangle.
 
  Node file is "baffle_nodes.txt".
  Element file is "baffle_elements.txt".
  Number of nodes =               512
 
  First 10 nodes
 
  Row         1             2       
  Col
 
    1    0.00000       1.00000    
    2    0.00000       1.37500    
    3    0.00000       1.75000    
    4    0.00000       2.12500    
    5    0.00000       2.50000    
    6    0.00000       2.87500    
    7    0.00000       3.25000    
    8    0.00000       3.62500    
    9    0.00000       4.00000    
   10    0.00000       4.37500    
 
  Element order =                   3
  Number of elements =            874
 
  First 10 elements
 
  Row       1      2      3
  Col
 
    1     317    306    298
    2      28      3     18
    3       4      3     28
    4      28     33      4
    5      72     69     57
    6      49     33     28
    7     114    106    122
    8      84     80     67
    9      88     69     72
   10     147    133    131
 
  Quadrature order =                 3
 
  Number of nonzero coefficients NZ_NUM =     3308

  Step        Residual

     1     1.94589    
     2     1.02565    
     3    0.411712    
     4    0.271570    
     5    0.143458    
     6    0.102652    
     7    0.490419E-01
     8    0.317833E-01
     9    0.164217E-01
    10    0.860515E-02
    11    0.392365E-02
    12    0.229199E-02
    13    0.156186E-02
    14    0.742249E-03
    15    0.399329E-03
    16    0.205418E-03
    17    0.124346E-03
    18    0.676339E-04
    19    0.322410E-04
    20    0.196990E-04
    21    0.134579E-04
    22    0.703567E-05
    23    0.352624E-05
    24    0.196816E-05
    25    0.107468E-05
    26    0.719786E-06
    27    0.424296E-06
    28    0.244519E-06
    29    0.135357E-06
    30    0.810820E-07
    31    0.470307E-07

  Number of iterations was   31
  Estimated error is   0.289709E-07
 
  Part of the solution vector U:
 
         1   0.0000000    
         2   0.0000000    
         3   0.0000000    
         4   0.0000000    
         5   0.0000000    
         6   0.0000000    
         7   0.0000000    
         8   0.0000000    
         9   0.0000000    
        10   0.0000000    
 
fem2d_poisson_cg():
  Wrote an ASCII file
    "baffle_values.txt"
  of the form
    U ( X(I), Y(I) )
  which can be used for plotting.
 
fem2d_poisson_cg():
  Normal end of execution.
 
30 November 2025   8:49:19.671 AM