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<html><head> <link rel="canonical" href="http://www.mcs.anl.gov/petsc/petsc-current/tutorials/HandsOnExercise.html" />
<title>PETSc Hands On</title>
</head><body>
<div id="version" align=right><b>petsc-3.7.5 2017-01-01</b></div>
<div id="bugreport" align=right><a href="mailto:petsc-maint@mcs.anl.gov?subject=Typo or Error in Documentation &body=Please describe the typo or error in the documentation: petsc-3.7.5 v3.7.5 tutorials/HandsOnExercise.html "><small>Report Typos and Errors</small></a></div>
<center>
<h2> PETSc Hands On</h2>
</center>
<p>
PETSc comes with a large number of example codes to illustrate usage. The three main sets are in:
<ul>
<li> ODEs - <a href="../src/ts/examples/tutorials/index.html">src/ts/examples/tutorials</a></li>
<li> Nonlinear problems - <a href="../src/snes/examples/tutorials/index.html">src/snes/examples/tutorials</a></li>
<li> Linear problems - <a href="../src/ksp/ksp/examples/tutorials/index.html">src/ksp/ksp/examples/tutorials</a></li>
</ul>
<!--------------------------------------------------------------------------->
<h2>Example 1: Linear Poisson equation on a 2D grid</h2>
<p>WHAT THIS EXAMPLE DEMONSTRATES:</p>
<ul>
<li>Using command line options</li>
<li>Using Linear Solvers</li>
<li>Handling a simple structured grid</li>
</ul>
<p>FURTHER DETAILS:</p>
<ul>
<li><a href="../src/ksp/ksp/examples/tutorials/ex50.c.html#line1">Mathematical description of the problem</a></li>
<li><a href="../src/ksp/ksp/examples/tutorials/ex50.c.html#line21">the source code</a></li>
</ul>
<p>DO THE FOLLOWING:</p>
<ul>
<li> Compile src/ksp/ksp/examples/tutorials/ex50.c
<pre>
cd petsc/src/ksp/ksp/examples/tutorials
make ex50
</pre>
</li>
<li> Run a 1 processor example with a 3x3 mesh and view the matrix assembled
<pre>
mpiexec -n 1 ./ex50 -da_grid_x 4 -da_grid_y 4 -mat_view <a href="../src/ksp/ksp/examples/tutorials/output/ex50_tut_1.out.html">[Expected output]</a>
</pre>
</li>
<li> Run with a 120x120 mesh on 16 processors using superlu_dist and view the solver options used
<pre>
mpiexec -n 16 ./ex50 -da_grid_x 120 -da_grid_y 120 -pc_type lu -pc_factor_mat_solver_package superlu_dist -ksp_monitor -ksp_view <a href="../src/ksp/ksp/examples/tutorials/output/ex50_tut_2.out.html">[Expected output]</a>
</pre>
</li>
<li> Run with a 2049x2049 grid using multigrid solver on 16 processors with 10 multigrid levels
<pre>
mpiexec -n 16 ./ex50 -da_grid_x 2049 -da_grid_y 2049 -pc_type mg -pc_mg_levels 10 -ksp_monitor <a href="../src/ksp/ksp/examples/tutorials/output/ex50_tut_3.out.html">[Expected output]</a>
</pre>
</li>
</ul>
<!--------------------------------------------------------------------------->
<h2>Example 2: Nonlinear ODE arising from a time-dependent one dimensional PDE</h2>
<p>WHAT THIS EXAMPLE DEMONSTRATES:</p>
<ul>
<li>Using command line options</li>
<li>Handling a simple structured grid</li>
<li>Using the ODE integrator</li>
<li>Using call-back functions</li>
</ul>
<p>FURTHER DETAILS:</p>
<ul>
<li><a href="../src/ts/examples/tutorials/ex2.c.html#line13">Mathematical description of the problem</a></li>
<li><a href="../src/ts/examples/tutorials/ex2.c.html#line36">the source code</a></li>
</ul>
<p>DO THE FOLLOWING:</p>
<ul>
<li> Compile src/ts/examples/tutorials/ex2.c
<pre>
cd petsc/src/ts/examples/tutorials
make ex2
</pre>
</li>
<li> Run a 1 processor example on the default grid with all the default solver options
<pre>
mpiexec -n 1 ./ex2 -ts_max_steps 10 -ts_monitor <a href="../src/ts/examples/tutorials/output/ex2_tut_1.out.html">[Expected output]</a>
</pre>
</li>
<li> Run with the same options on 4 processors plus monitor convergence of the nonlinear and linear solvers
<pre>
mpiexec -n 4 ./ex2 -ts_max_steps 10 -ts_monitor -snes_monitor -ksp_monitor <a href="../src/ts/examples/tutorials/output/ex2_tut_2.out.html">[Expected output]</a>
</pre>
</li>
<li> Run with the same options on 16 processors with 128 grid points
<pre>
mpiexec -n 16 ./ex2 -ts_max_steps 10 -ts_monitor -M 128 <a href="../src/ts/examples/tutorials/output/ex2_tut_3.out.html">[Expected output]</a>
</pre>
</li>
</ul>
<!--------------------------------------------------------------------------->
<h2>Example 3: Nonlinear PDE on a structured grid</h2>
<p>WHAT THIS EXAMPLE DEMONSTRATES:</p>
<ul>
<li>Handling a 2d structured grid</li>
<li>Using the nonlinear solvers</li>
<li>Changing the default linear solver</li>
</ul>
<p>FURTHER DETAILS:</p>
<ul>
<li><a href="../src/snes/examples/tutorials/ex19.c.html#line19">Mathematical description of the problem</a></li>
<li><a href="../src/snes/examples/tutorials/ex19.c.html#line94">main program source code</a></li>
<li><a href="../src/snes/examples/tutorials/ex19.c.html#line246">physics source code</a></li>
</ul>
<p>DO THE FOLLOWING:</p>
<ul>
<li> Compile src/snes/examples/tutorials/ex19.c
<pre>
cd petsc/src/snes/examples/tutorials/
make ex19
</pre>
</li>
<li> Run a 16 processor example with six levels of grid refinement, monitor the convergence of the nonlinear and linear solver
and examine the exact solver used
<pre>
mpiexec -n 16 ./ex19 -da_refine 6 -snes_monitor -ksp_monitor -snes_view <a href="../src/snes/examples/tutorials/output/ex19_tut_1.out.html">[Expected output]</a>
</pre>
</li>
<li> Run with the same options but use geometric multigrid as the linear solver
<pre>
mpiexec -n 16 ./ex19 -da_refine 6 -snes_monitor -ksp_monitor -snes_view -pc_type mg <a href="../src/snes/examples/tutorials/output/ex19_tut_2.out.html">[Expected output]</a>
</pre>
Note this requires many fewer iterations than the default solver
</li>
<li> Run with the same options but use algebraic multigrid (hypre's BoomerAMG) as the linear solver
<pre>
mpiexec -n 16 ./ex19 -da_refine 6 -snes_monitor -ksp_monitor -snes_view -pc_type hypre <a href="../src/snes/examples/tutorials/output/ex19_tut_3.out.html">[Expected output]</a>
</pre>
Note this requires many fewer iterations than the default solver but requires more iterations than geometric multigrid
</li>
<li> Run on 4 processors with the default linear solver and profile the run
<pre>
mpiexec -n 4 ./ex19 -da_refine 6 -log_summary <a href="../src/snes/examples/tutorials/output/ex19_tut_4.out.html">[Expected output]</a>
</pre>
Search for the line beginning with SNESSolve, the fourth column gives the time for the nonlinear solve.
</li>
<li> Run on 4 processors with the geometric multigrid linear solver and profile the run
<pre>
mpiexec -n 4 ./ex19 -da_refine 6 -log_summary -pc_type mg <a href="../src/snes/examples/tutorials/output/ex19_tut_5.out.html">[Expected output]</a>
</pre>
Compare the runtime for SNESSolve to the case with the default solver
</li>
<li> Run on 16 processors with the default linear solver and profile the run
<pre>
mpiexec -n 16 ./ex19 -da_refine 6 -log_summary <a href="../src/snes/examples/tutorials/output/ex19_tut_6.out.html">[Expected output]</a>
</pre>
Compare the runtime for SNESSolve to the 4 processor case with the default solver, what is the speedup?
</li>
<li> Run on 16 processors with the geometric multigrid linear solver and profile the run
<pre>
mpiexec -n 16 ./ex19 -da_refine 6 -log_summary -pc_type mg <a href="../src/snes/examples/tutorials/output/ex19_tut_7.out.html">[Expected output]</a>
</pre>
Compare the runtime for the SNESSolve to the 4 processor case with multigrid, what is the speedup?
Why is the speedup for multigrid lower than the speedup for the default solver?
</li>
</ul>
<!--------------------------------------------------------------------------->
<h2>Example 4: Linear Stokes-type PDE on a structured grid</h2>
<p>WHAT THIS EXAMPLE DEMONSTRATES:</p>
<ul>
<li>Handling a 3d structured grid</li>
<li>Controlling linear solver options</li>
<li>Selecting composible preconditioners</li>
<li>Solving a Stokes problem</li>
<li>Adding your own problem specific visualization</li>
</ul>
<p>FURTHER DETAILS:</p>
<ul>
<li><a href="../src/ksp/ksp/examples/tutorials/ex42.c.html">Mathematical description of the problem</a></li>
<li><a href="../src/ksp/ksp/examples/tutorials/ex42.c.html#line2059">main program source code</a></li>
<li><a href="../src/ksp/ksp/examples/tutorials/ex42.c.html#line819">physics source code</a></li>
</ul>
<p>DO THE FOLLOWING:</p>
<ul>
<li> Compile src/ksp/ksp/examples/tutorials/ex42.c
<pre>
cd petsc/src/ksp/ksp/examples/tutorials
make ex42
</pre>
</li>
<li> Solve with the default solver
<pre>
mpiexec -n 4 ./ex42 -stokes_ksp_monitor <a href="../src/ksp/ksp/examples/tutorials/output/ex42_tut_1.out.html">[Expected output]</a>
</pre>
Note the poor convergence for even a very small problem
</li>
<li> Solve with a solver appropriate for Stoke's problems -stokes_pc_type fieldsplit -stokes_pc_fieldsplit_type schur
<pre>
mpiexec -n 4 ./ex42 -stokes_ksp_monitor -stokes_pc_type fieldsplit -stokes_pc_fieldsplit_type schur <a href="../src/ksp/ksp/examples/tutorials/output/ex42_tut_2.out.html">[Expected output]</a>
</pre>
</li>
<li> Solve with a finer mesh
<pre>
mpiexec -n 16 ./ex42 -mx 40 -stokes_ksp_monitor -stokes_pc_type fieldsplit -stokes_pc_fieldsplit_type schur <a href="../src/ksp/ksp/examples/tutorials/output/ex42_tut_3.out.html">[Expected output]</a>
</pre>
</li>
</ul>
<!--------------------------------------------------------------------------->
<h2>Example 5: Nonlinear time dependent PDE on Unstructured Grid</h2>
<p>WHAT THIS EXAMPLE DEMONSTRATES:</p>
<ul>
<li>Changing the default ODE integrator</li>
<li>Handling unstructured grids</li>
<li>Registering your own interchangeable physics and algorithm modules</li>
</ul>
<p>FURTHER DETAILS:</p>
<ul>
<li><a href="../src/ts/examples/tutorials/ex11.c.html">Mathematical description of the problem</a></li>
<li><a href="../src/ts/examples/tutorials/ex11.c.html#line1403">main program source code</a></li>
<li><a href="../src/ts/examples/tutorials/ex11.c.html#line186">source code of physics modules</a></li>
</ul>
<p>DO THE FOLLOWING:</p>
<ul>
<li> Compile src/ts/examples/tutorials/ex11.c
<pre>
cd petsc/src/ts/examples/tutorials
make ex11
</pre>
<li>Run simple advection through a tiny hybrid mesh
<pre>
mpiexec -n 1 ./ex11 -f ${PETSC_DIR}/share/petsc/datafiles/meshes/sevenside.exo <a href="../src/ts/examples/tutorials/output/ex11_tut_1.out.html">[Expected output]</a>
</pre>
</li>
<li>Run simple advection through a small mesh with a Rosenbrock-W solver
<pre>
mpiexec -n 1 ./ex11 -f ${PETSC_DIR}/share/petsc/datafiles/meshes/sevenside.exo -ts_type rosw <a href="../src/ts/examples/tutorials/output/ex11_tut_2.out.html">[Expected output]</a>
</pre>
</li>
<li>Run simple advection through a larger quadrilateral mesh of an annulus with least squares reconstruction and no limiting, monitoring the error
<pre>
mpiexec -n 16 ./ex11 -f ${PETSC_DIR}/share/petsc/datafiles/meshes/annulus-20.exo -monitor Error -advect_sol_type bump -petscfv_type leastsquares -petsclimiter_type sin <a href="../src/ts/examples/tutorials/output/ex11_tut_4.out.html">[Expected output]</a>
</pre>
Compare turning to the error after turning off reconstruction.
</li>
<li>Run shallow water on the larger mesh with least squares reconstruction and minmod limiting, monitoring water Height (integral is conserved) and Energy (not conserved)
<pre>
mpiexec -n 4 ./ex11 -f ${PETSC_DIR}/share/petsc/datafiles/meshes/annulus-20.exo -physics sw -monitor Height,Energy -petscfv_type leastsquares -petsclimiter_type minmod <a href="../src/ts/examples/tutorials/output/ex11_tut_5.out.html">[Expected output]</a>
</pre>
</li>
</ul>
</body></html>
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