1 static char help[] = "Solves the trivial ODE 2 du/dt = 1, u(0) = 0. \n\n"; 2 3 #include <petscts.h> 4 #include <petscpc.h> 5 6 PetscErrorCode IFunction(TS,PetscReal,Vec,Vec,Vec,void*); 7 PetscErrorCode IJacobian(TS,PetscReal,Vec,Vec,PetscReal,Mat,Mat,void*); 8 9 int main(int argc,char **argv) 10 { 11 TS ts; 12 Vec x; 13 Vec f; 14 Mat A; 15 16 PetscFunctionBeginUser; 17 PetscCall(PetscInitialize(&argc,&argv,(char*)0,help)); 18 19 PetscCall(TSCreate(PETSC_COMM_WORLD,&ts)); 20 PetscCall(TSSetEquationType(ts,TS_EQ_ODE_IMPLICIT)); 21 PetscCall(VecCreate(PETSC_COMM_WORLD,&f)); 22 PetscCall(VecSetSizes(f,1,PETSC_DECIDE)); 23 PetscCall(VecSetFromOptions(f)); 24 PetscCall(VecSetUp(f)); 25 PetscCall(TSSetIFunction(ts,f,IFunction,NULL)); 26 PetscCall(VecDestroy(&f)); 27 28 PetscCall(MatCreate(PETSC_COMM_WORLD,&A)); 29 PetscCall(MatSetSizes(A,1,1,PETSC_DECIDE,PETSC_DECIDE)); 30 PetscCall(MatSetFromOptions(A)); 31 PetscCall(MatSetUp(A)); 32 PetscCall(MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY)); 33 PetscCall(MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY)); 34 /* ensure that the Jacobian matrix has diagonal entries since that is required by TS */ 35 PetscCall(MatShift(A,(PetscReal)1)); 36 PetscCall(MatShift(A,(PetscReal)-1)); 37 PetscCall(TSSetIJacobian(ts,A,A,IJacobian,NULL)); 38 PetscCall(MatDestroy(&A)); 39 40 PetscCall(VecCreate(PETSC_COMM_WORLD,&x)); 41 PetscCall(VecSetSizes(x,1,PETSC_DECIDE)); 42 PetscCall(VecSetFromOptions(x)); 43 PetscCall(VecSetUp(x)); 44 PetscCall(TSSetSolution(ts,x)); 45 PetscCall(VecDestroy(&x)); 46 PetscCall(TSSetFromOptions(ts)); 47 48 PetscCall(TSSetStepNumber(ts,0)); 49 PetscCall(TSSetTimeStep(ts,1)); 50 PetscCall(TSSetTime(ts,0)); 51 PetscCall(TSSetMaxTime(ts,PETSC_MAX_REAL)); 52 PetscCall(TSSetMaxSteps(ts,3)); 53 54 /* 55 When an ARKIMEX scheme with an explicit stage is used this will error with a message informing the user it is not possible to use 56 a non-trivial mass matrix with ARKIMEX schemes with explicit stages. 57 */ 58 PetscCall(TSSolve(ts,NULL)); 59 60 PetscCall(TSDestroy(&ts)); 61 PetscCall(PetscFinalize()); 62 return 0; 63 } 64 65 PetscErrorCode IFunction(TS ts,PetscReal t,Vec x,Vec xdot,Vec f,void *ctx) 66 { 67 PetscFunctionBeginUser; 68 PetscCall(VecCopy(xdot,f)); 69 PetscCall(VecScale(f,2.0)); 70 PetscCall(VecShift(f,-1.0)); 71 PetscFunctionReturn(0); 72 } 73 74 PetscErrorCode IJacobian(TS ts,PetscReal t,Vec x,Vec xdot,PetscReal shift,Mat A,Mat B,void *ctx) 75 { 76 PetscScalar j; 77 78 PetscFunctionBeginUser; 79 j = shift*2.0; 80 PetscCall(MatSetValue(B,0,0,j,INSERT_VALUES)); 81 PetscCall(MatAssemblyBegin(B,MAT_FINAL_ASSEMBLY)); 82 PetscCall(MatAssemblyEnd(B,MAT_FINAL_ASSEMBLY)); 83 PetscFunctionReturn(0); 84 } 85 86 /*TEST 87 88 test: 89 suffix: arkimex_explicit_stage 90 requires: !defined(PETSCTEST_VALGRIND) defined(PETSC_USE_DEBUG) 91 args: -ts_type arkimex -petsc_ci_portable_error_output -error_output_stdout 92 filter: egrep -v "(options_left|memory block|leaked context|is not freed before MPI_Finalize|Could be the program crashed)" 93 94 test: 95 suffix: arkimex_implicit_stage 96 args: -ts_type arkimex -ts_arkimex_type l2 -ts_monitor_solution -ts_monitor 97 98 TEST*/ 99