<div dir="ltr"><p style="margin-top:0px;font-family:Helvetica,Arial,sans-serif;font-size:15px">Hello,</p><p style="font-family:Helvetica,Arial,sans-serif;font-size:15px">I am using PETSc with FEniCS project libraries to solve a nonlinear problem. I am using PETSc Krylov solver with the following configuration</p><p style="font-family:Helvetica,Arial,sans-serif;font-size:15px"><span style="font-family:Consolas,Menlo,Monaco,"Lucida Console","Liberation Mono","DejaVu Sans Mono","Bitstream Vera Sans Mono","Courier New",monospace;white-space:pre;background-color:rgb(249,249,249)">pc = PETScPreconditioner("petsc_amg") 
PETScOptions.set("mg_levels_ksp_type", "chebyshev")
PETScOptions.set("mg_levels_pc_type", "jacobi")
PETScOptions.set("mg_levels_esteig_ksp_type", "cg")
PETScOptions.set("mg_levels_ksp_chebyshev_esteig_steps", 50)
solver_u = PETScKrylovSolver("cg", pc)
</span><br></p><p style="font-size:15px"><span style="font-family:Helvetica,Arial,sans-serif">I am encountering this error sometimes during the solution of the linear system:</span></p><span style="font-family:Consolas,Menlo,Monaco,"Lucida Console","Liberation Mono","DejaVu Sans Mono","Bitstream Vera Sans Mono","Courier New",monospace;font-size:15px;white-space:pre;background-color:rgb(249,249,249)">Error:   Unable to successfully call PETSc function 'KSPSolve'.
*** Reason:  PETSc error code is: 77 (Petsc has generated inconsistent data).
*** Where:   This error was encountered inside /tmp/dolfin/dolfin/la/PETScKrylovSolver.cpp. </span><p style="font-size:15px"><span style="background-color:rgb(249,249,249);font-family:Consolas,Menlo,Monaco,"Lucida Console","Liberation Mono","DejaVu Sans Mono","Bitstream Vera Sans Mono","Courier New",monospace;white-space:pre">*** Process: 130</span></p><p style="font-size:15px">Can anybody help me in understanding the possible reasons for this error code? Or refer me to any available documentation? It will be really helpful. </p><p style="font-size:15px">Also, I will like to know if there is a way to <span style="font-family:Helvetica,Arial,sans-serif">prevent the code from stopping due to such PETSc errors, so that I can tweak some parameters to hopefully make it progress.</span>  </p><div><br></div><div>Thanks and Regards,</div><div>Aditya</div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><br></div></div></div></div></div></div>