Dear all,

    the following output from -snes_test_jacobian_view lokks clear enough to pinpoint my mistake (I must be putting jacobian elements in the wrong place), but it nevertheless left me suprised.

0 SNES Function norm 2.945516399303e-01
  ---------- Testing Jacobian -------------
  Testing hand-coded Jacobian, if (for double precision runs) ||J - Jfd||_F/||J||_F is
    O(1.e-8), the hand-coded Jacobian is probably correct.
  ||J - Jfd||_F/||J||_F = 0.000121529, ||J - Jfd||_F = 0.395752
  Hand-coded Jacobian ----------
Mat Object: 4 MPI processes
  row 84:     (84, 60.)      (85, 0.)      (3446, -80.)      (3447, 0.)      (6808, 20.)      (6809, 0.)     
  row 85:     (84, 0.00914434)      (85, 1.)      (3446, 0.)      (3447, 0.)      (6808, 0.)      (6809, 0.)    
    
   Finite difference Jacobian ----------
Mat Object: 4 MPI processes
  type: mpiaij
  row 84:   (84, 60.)    (1806, -80.)    (3528, 20.)   
  row 85:   (85, 0.999971)

  Hand-coded minus finite-difference Jacobian with tolerance 1e-05 ----------
Mat Object: 4 MPI processes
  type: mpiaij
  row 84:  
  row 85:   (84, 0.00914434)    (85, 2.9293e-05)

The difference of the two matrices shoudl be nonzero in row 84 for all elements 1806, 3528, 3446, 6808. Is it intended that the difference is shown only for matrix elements that are present in both the hand-coded and the FD jacobian?

I would have expected an output like

row 84: (1806,80.)   (3446,-80.), etc

(This was on  PETSc Release Version 3.24.2)

Thanks

    Matteo

-- 
Prof. Matteo Semplice
Università degli Studi dell’Insubria
Dipartimento di Scienza e Alta Tecnologia – DiSAT
Professore Associato
Via Valleggio, 11 – 22100 Como (CO) – Italia
tel.: +39 031 2386316