Actual source code: ex5f90.F90
1: !
2: ! Description: Solves a nonlinear system in parallel with SNES.
3: ! We solve the Bratu (SFI - solid fuel ignition) problem in a 2D rectangular
4: ! domain, using distributed arrays (DMDAs) to partition the parallel grid.
5: ! The command line options include:
6: ! -par <parameter>, where <parameter> indicates the nonlinearity of the problem
7: ! problem SFI: <parameter> = Bratu parameter (0 <= par <= 6.81)
8: !
10: !
11: ! --------------------------------------------------------------------------
12: !
13: ! Solid Fuel Ignition (SFI) problem. This problem is modeled by
14: ! the partial differential equation
15: !
16: ! -Laplacian u - lambda*exp(u) = 0, 0 < x,y < 1,
17: !
18: ! with boundary conditions
19: !
20: ! u = 0 for x = 0, x = 1, y = 0, y = 1.
21: !
22: ! A finite difference approximation with the usual 5-point stencil
23: ! is used to discretize the boundary value problem to obtain a nonlinear
24: ! system of equations.
25: !
26: ! The uniprocessor version of this code is snes/tutorials/ex4f.F
27: !
28: ! --------------------------------------------------------------------------
29: ! The following define must be used before including any PETSc include files
30: ! into a module or interface. This is because they can't handle declarations
31: ! in them
32: !
33: #include <petsc/finclude/petscsnes.h>
34: #include <petsc/finclude/petscdmda.h>
35: module ex5f90module
36: use petscsnes
37: use petscdmda
38: implicit none
39: type userctx
40: PetscInt xs, xe, xm, gxs, gxe, gxm
41: PetscInt ys, ye, ym, gys, gye, gym
42: PetscInt mx, my
43: PetscMPIInt rank
44: PetscReal lambda
45: end type userctx
47: interface
48: subroutine SNESSetApplicationContext(snes, ctx, ierr)
49: use petscsnes
50: import userctx
51: implicit none
52: SNES snes
53: type(userctx) ctx
54: PetscErrorCode ierr
55: end subroutine
56: subroutine SNESGetApplicationContext(snes, ctx, ierr)
57: use petscsnes
58: import userctx
59: implicit none
60: SNES snes
61: type(userctx), pointer :: ctx
62: PetscErrorCode ierr
63: end subroutine
64: end interface
66: contains
67: ! ---------------------------------------------------------------------
68: !
69: ! FormFunction - Evaluates nonlinear function, F(x).
70: !
71: ! Input Parameters:
72: ! snes - the SNES context
73: ! X - input vector
74: ! dummy - optional user-defined context, as set by SNESSetFunction()
75: ! (not used here)
76: !
77: ! Output Parameter:
78: ! F - function vector
79: !
80: ! Notes:
81: ! This routine serves as a wrapper for the lower-level routine
82: ! "FormFunctionLocal", where the actual computations are
83: ! done using the standard Fortran style of treating the local
84: ! vector data as a multidimensional array over the local mesh.
85: ! This routine merely handles ghost point scatters and accesses
86: ! the local vector data via VecGetArray() and VecRestoreArray().
87: !
88: subroutine FormFunction(snes, X, F, user, ierr)
89: implicit none
91: ! Input/output variables:
92: SNES snes
93: Vec X, F
94: PetscErrorCode ierr
95: type(userctx) user
96: DM da
98: ! Declarations for use with local arrays:
99: PetscScalar, pointer :: lx_v(:), lf_v(:)
100: Vec localX
102: ! Scatter ghost points to local vector, using the 2-step process
103: ! DMGlobalToLocalBegin(), DMGlobalToLocalEnd().
104: ! By placing code between these two statements, computations can
105: ! be done while messages are in transition.
106: PetscCall(SNESGetDM(snes, da, ierr))
107: PetscCall(DMGetLocalVector(da, localX, ierr))
108: PetscCall(DMGlobalToLocalBegin(da, X, INSERT_VALUES, localX, ierr))
109: PetscCall(DMGlobalToLocalEnd(da, X, INSERT_VALUES, localX, ierr))
111: ! Get a pointer to vector data.
112: ! - For default PETSc vectors, VecGetArray() returns a pointer to
113: ! the data array. Otherwise, the routine is implementation dependent.
114: ! - You MUST call VecRestoreArray() when you no longer need access to
115: ! the array.
116: ! - Note that the interface to VecGetArray() differs from VecGetArray().
118: PetscCall(VecGetArray(localX, lx_v, ierr))
119: PetscCall(VecGetArray(F, lf_v, ierr))
121: ! Compute function over the locally owned part of the grid
122: PetscCall(FormFunctionLocal(lx_v, lf_v, user, ierr))
124: ! Restore vectors
125: PetscCall(VecRestoreArray(localX, lx_v, ierr))
126: PetscCall(VecRestoreArray(F, lf_v, ierr))
128: ! Insert values into global vector
130: PetscCall(DMRestoreLocalVector(da, localX, ierr))
131: PetscCall(PetscLogFlops(11.0d0*user%ym*user%xm, ierr))
133: ! PetscCallA(VecView(X,PETSC_VIEWER_STDOUT_WORLD,ierr))
134: ! PetscCallA(VecView(F,PETSC_VIEWER_STDOUT_WORLD,ierr))
135: end subroutine formfunction
137: ! ---------------------------------------------------------------------
138: !
139: ! FormInitialGuess - Forms initial approximation.
140: !
141: ! Input Parameters:
142: ! X - vector
143: !
144: ! Output Parameter:
145: ! X - vector
146: !
147: ! Notes:
148: ! This routine serves as a wrapper for the lower-level routine
149: ! "InitialGuessLocal", where the actual computations are
150: ! done using the standard Fortran style of treating the local
151: ! vector data as a multidimensional array over the local mesh.
152: ! This routine merely handles ghost point scatters and accesses
153: ! the local vector data via VecGetArray() and VecRestoreArray().
154: !
155: subroutine FormInitialGuess(snes, X, ierr)
156: ! Input/output variables:
157: SNES snes
158: type(userctx), pointer:: puser
159: Vec X
160: PetscErrorCode ierr
161: DM da
163: ! Declarations for use with local arrays:
164: PetscScalar, pointer :: lx_v(:)
166: ierr = 0
167: PetscCallA(SNESGetDM(snes, da, ierr))
168: PetscCallA(SNESGetApplicationContext(snes, puser, ierr))
169: ! Get a pointer to vector data.
170: ! - For default PETSc vectors, VecGetArray() returns a pointer to
171: ! the data array. Otherwise, the routine is implementation dependent.
172: ! - You MUST call VecRestoreArray() when you no longer need access to
173: ! the array.
174: ! - Note that the interface to VecGetArray() differs from VecGetArray().
176: PetscCallA(VecGetArray(X, lx_v, ierr))
178: ! Compute initial guess over the locally owned part of the grid
179: PetscCallA(InitialGuessLocal(puser, lx_v, ierr))
181: ! Restore vector
182: PetscCallA(VecRestoreArray(X, lx_v, ierr))
184: ! Insert values into global vector
186: end
188: ! ---------------------------------------------------------------------
189: !
190: ! InitialGuessLocal - Computes initial approximation, called by
191: ! the higher level routine FormInitialGuess().
192: !
193: ! Input Parameter:
194: ! x - local vector data
195: !
196: ! Output Parameters:
197: ! x - local vector data
198: ! ierr - error code
199: !
200: ! Notes:
201: ! This routine uses standard Fortran-style computations over a 2-dim array.
202: !
203: subroutine InitialGuessLocal(user, x, ierr)
204: ! Input/output variables:
205: type(userctx) user
206: PetscScalar x(user%xs:user%xe, user%ys:user%ye)
207: PetscErrorCode ierr
209: ! Local variables:
210: PetscInt i, j
211: PetscReal temp1, temp, hx, hy
212: PetscReal one
214: ! Set parameters
216: ierr = 0
217: one = 1.0
218: hx = one/(user%mx - 1)
219: hy = one/(user%my - 1)
220: temp1 = user%lambda/(user%lambda + one)
222: do j = user%ys, user%ye
223: temp = min(j - 1, user%my - j)*hy
224: do i = user%xs, user%xe
225: if (i == 1 .or. j == 1 .or. i == user%mx .or. j == user%my) then
226: x(i, j) = 0.0
227: else
228: x(i, j) = temp1*sqrt(min(hx*min(i - 1, user%mx - i), temp))
229: end if
230: end do
231: end do
233: end
235: ! ---------------------------------------------------------------------
236: !
237: ! FormFunctionLocal - Computes nonlinear function, called by
238: ! the higher level routine FormFunction().
239: !
240: ! Input Parameter:
241: ! x - local vector data
242: !
243: ! Output Parameters:
244: ! f - local vector data, f(x)
245: ! ierr - error code
246: !
247: ! Notes:
248: ! This routine uses standard Fortran-style computations over a 2-dim array.
249: !
250: subroutine FormFunctionLocal(x, f, user, ierr)
251: ! Input/output variables:
252: type(userctx) user
253: PetscScalar x(user%gxs:user%gxe, user%gys:user%gye)
254: PetscScalar f(user%xs:user%xe, user%ys:user%ye)
255: PetscErrorCode ierr
257: ! Local variables:
258: PetscScalar two, one, hx, hy, hxdhy, hydhx, sc
259: PetscScalar u, uxx, uyy
260: PetscInt i, j
262: one = 1.0
263: two = 2.0
264: hx = one/(user%mx - 1)
265: hy = one/(user%my - 1)
266: sc = hx*hy*user%lambda
267: hxdhy = hx/hy
268: hydhx = hy/hx
270: ! Compute function over the locally owned part of the grid
272: do j = user%ys, user%ye
273: do i = user%xs, user%xe
274: if (i == 1 .or. j == 1 .or. i == user%mx .or. j == user%my) then
275: f(i, j) = x(i, j)
276: else
277: u = x(i, j)
278: uxx = hydhx*(two*u - x(i - 1, j) - x(i + 1, j))
279: uyy = hxdhy*(two*u - x(i, j - 1) - x(i, j + 1))
280: f(i, j) = uxx + uyy - sc*exp(u)
281: end if
282: end do
283: end do
285: end
287: ! ---------------------------------------------------------------------
288: !
289: ! FormJacobian - Evaluates Jacobian matrix.
290: !
291: ! Input Parameters:
292: ! snes - the SNES context
293: ! x - input vector
294: ! dummy - optional user-defined context, as set by SNESSetJacobian()
295: ! (not used here)
296: !
297: ! Output Parameters:
298: ! jac - Jacobian matrix
299: ! jac_prec - optionally different matrix used to construct the preconditioner (not used here)
300: !
301: ! Notes:
302: ! This routine serves as a wrapper for the lower-level routine
303: ! "FormJacobianLocal", where the actual computations are
304: ! done using the standard Fortran style of treating the local
305: ! vector data as a multidimensional array over the local mesh.
306: ! This routine merely accesses the local vector data via
307: ! VecGetArray() and VecRestoreArray().
308: !
309: ! Notes:
310: ! Due to grid point reordering with DMDAs, we must always work
311: ! with the local grid points, and then transform them to the new
312: ! global numbering with the "ltog" mapping
313: ! We cannot work directly with the global numbers for the original
314: ! uniprocessor grid!
315: !
316: ! Two methods are available for imposing this transformation
317: ! when setting matrix entries:
318: ! (A) MatSetValuesLocal(), using the local ordering (including
319: ! ghost points!)
320: ! - Set matrix entries using the local ordering
321: ! by calling MatSetValuesLocal()
322: ! (B) MatSetValues(), using the global ordering
324: ! - Set matrix entries using the global ordering by calling
325: ! MatSetValues()
326: ! Option (A) seems cleaner/easier in many cases, and is the procedure
327: ! used in this example.
328: !
329: subroutine FormJacobian(snes, X, jac, jac_prec, user, ierr)
330: ! Input/output variables:
331: SNES snes
332: Vec X
333: Mat jac, jac_prec
334: type(userctx) user
335: PetscErrorCode ierr
336: DM da
338: ! Declarations for use with local arrays:
339: PetscScalar, pointer :: lx_v(:)
340: Vec localX
342: ! Scatter ghost points to local vector, using the 2-step process
343: ! DMGlobalToLocalBegin(), DMGlobalToLocalEnd()
344: ! Computations can be done while messages are in transition,
345: ! by placing code between these two statements.
347: PetscCallA(SNESGetDM(snes, da, ierr))
348: PetscCallA(DMGetLocalVector(da, localX, ierr))
349: PetscCallA(DMGlobalToLocalBegin(da, X, INSERT_VALUES, localX, ierr))
350: PetscCallA(DMGlobalToLocalEnd(da, X, INSERT_VALUES, localX, ierr))
352: ! Get a pointer to vector data
353: PetscCallA(VecGetArray(localX, lx_v, ierr))
355: ! Compute entries for the locally owned part of the Jacobian preconditioner.
356: PetscCallA(FormJacobianLocal(lx_v, jac_prec, user, ierr))
358: ! Assemble matrix, using the 2-step process:
359: ! MatAssemblyBegin(), MatAssemblyEnd()
360: ! Computations can be done while messages are in transition,
361: ! by placing code between these two statements.
363: PetscCallA(MatAssemblyBegin(jac, MAT_FINAL_ASSEMBLY, ierr))
364: if (jac /= jac_prec) then
365: PetscCallA(MatAssemblyBegin(jac_prec, MAT_FINAL_ASSEMBLY, ierr))
366: end if
367: PetscCallA(VecRestoreArray(localX, lx_v, ierr))
368: PetscCallA(DMRestoreLocalVector(da, localX, ierr))
369: PetscCallA(MatAssemblyEnd(jac, MAT_FINAL_ASSEMBLY, ierr))
370: if (jac /= jac_prec) then
371: PetscCallA(MatAssemblyEnd(jac_prec, MAT_FINAL_ASSEMBLY, ierr))
372: end if
374: ! Tell the matrix we will never add a new nonzero location to the
375: ! matrix. If we do it will generate an error.
377: PetscCallA(MatSetOption(jac, MAT_NEW_NONZERO_LOCATION_ERR, PETSC_TRUE, ierr))
379: end
381: ! ---------------------------------------------------------------------
382: !
383: ! FormJacobianLocal - Computes Jacobian matrix used to compute the preconditioner,
384: ! called by the higher level routine FormJacobian().
385: !
386: ! Input Parameters:
387: ! x - local vector data
388: !
389: ! Output Parameters:
390: ! jac_prec - Jacobian matrix used to compute the preconditioner
391: ! ierr - error code
392: !
393: ! Notes:
394: ! This routine uses standard Fortran-style computations over a 2-dim array.
395: !
396: ! Notes:
397: ! Due to grid point reordering with DMDAs, we must always work
398: ! with the local grid points, and then transform them to the new
399: ! global numbering with the "ltog" mapping
400: ! We cannot work directly with the global numbers for the original
401: ! uniprocessor grid!
402: !
403: ! Two methods are available for imposing this transformation
404: ! when setting matrix entries:
405: ! (A) MatSetValuesLocal(), using the local ordering (including
406: ! ghost points!)
407: ! - Set matrix entries using the local ordering
408: ! by calling MatSetValuesLocal()
409: ! (B) MatSetValues(), using the global ordering
410: ! - Then apply this map explicitly yourself
411: ! - Set matrix entries using the global ordering by calling
412: ! MatSetValues()
413: ! Option (A) seems cleaner/easier in many cases, and is the procedure
414: ! used in this example.
415: !
416: subroutine FormJacobianLocal(x, jac_prec, user, ierr)
417: ! Input/output variables:
418: type(userctx) user
419: PetscScalar x(user%gxs:user%gxe, user%gys:user%gye)
420: Mat jac_prec
421: PetscErrorCode ierr
423: ! Local variables:
424: PetscInt row, col(5), i, j
425: PetscInt ione, ifive
426: PetscScalar two, one, hx, hy, hxdhy
427: PetscScalar hydhx, sc, v(5)
429: ! Set parameters
430: ione = 1
431: ifive = 5
432: one = 1.0
433: two = 2.0
434: hx = one/(user%mx - 1)
435: hy = one/(user%my - 1)
436: sc = hx*hy
437: hxdhy = hx/hy
438: hydhx = hy/hx
440: ! Compute entries for the locally owned part of the Jacobian.
441: ! - Currently, all PETSc parallel matrix formats are partitioned by
442: ! contiguous chunks of rows across the processors.
443: ! - Each processor needs to insert only elements that it owns
444: ! locally (but any non-local elements will be sent to the
445: ! appropriate processor during matrix assembly).
446: ! - Here, we set all entries for a particular row at once.
447: ! - We can set matrix entries either using either
448: ! MatSetValuesLocal() or MatSetValues(), as discussed above.
449: ! - Note that MatSetValues() uses 0-based row and column numbers
450: ! in Fortran as well as in C.
452: do j = user%ys, user%ye
453: row = (j - user%gys)*user%gxm + user%xs - user%gxs - 1
454: do i = user%xs, user%xe
455: row = row + 1
456: ! boundary points
457: if (i == 1 .or. j == 1 .or. i == user%mx .or. j == user%my) then
458: col(1) = row
459: v(1) = one
460: PetscCallA(MatSetValuesLocal(jac_prec, ione, [row], ione, col, v, INSERT_VALUES, ierr))
461: ! interior grid points
462: else
463: v(1) = -hxdhy
464: v(2) = -hydhx
465: v(3) = two*(hydhx + hxdhy) - sc*user%lambda*exp(x(i, j))
466: v(4) = -hydhx
467: v(5) = -hxdhy
468: col(1) = row - user%gxm
469: col(2) = row - 1
470: col(3) = row
471: col(4) = row + 1
472: col(5) = row + user%gxm
473: PetscCallA(MatSetValuesLocal(jac_prec, ione, [row], ifive, col, v, INSERT_VALUES, ierr))
474: end if
475: end do
476: end do
478: end
480: end module ex5f90module
482: program main
483: use ex5f90module
484: implicit none
485: !
487: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
488: ! Variable declarations
489: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
490: !
491: ! Variables:
492: ! snes - nonlinear solver
493: ! x, r - solution, residual vectors
494: ! J - Jacobian matrix
495: ! its - iterations for convergence
496: ! Nx, Ny - number of preocessors in x- and y- directions
497: ! matrix_free - flag - 1 indicates matrix-free version
498: !
499: SNES snes
500: Vec x, r
501: Mat J
502: PetscErrorCode ierr
503: PetscInt its
504: PetscBool flg, matrix_free
505: PetscInt ione, nfour
506: PetscReal lambda_max, lambda_min
507: type(userctx) user
508: DM da
510: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
511: ! Initialize program
512: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
513: PetscCallA(PetscInitialize(ierr))
514: PetscCallMPIA(MPI_Comm_rank(PETSC_COMM_WORLD, user%rank, ierr))
516: ! Initialize problem parameters
517: lambda_max = 6.81
518: lambda_min = 0.0
519: user%lambda = 6.0
520: ione = 1
521: nfour = 4
522: PetscCallA(PetscOptionsGetReal(PETSC_NULL_OPTIONS, PETSC_NULL_CHARACTER, '-par', user%lambda, flg, ierr))
523: PetscCheckA(user%lambda < lambda_max .and. user%lambda > lambda_min, PETSC_COMM_SELF, PETSC_ERR_USER, 'Lambda provided with -par is out of range')
525: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
526: ! Create nonlinear solver context
527: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
528: PetscCallA(SNESCreate(PETSC_COMM_WORLD, snes, ierr))
530: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
531: ! Create vector data structures; set function evaluation routine
532: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
534: ! Create distributed array (DMDA) to manage parallel grid and vectors
536: ! This really needs only the star-type stencil, but we use the box
537: ! stencil temporarily.
538: PetscCallA(DMDACreate2d(PETSC_COMM_WORLD, DM_BOUNDARY_NONE, DM_BOUNDARY_NONE, DMDA_STENCIL_BOX, nfour, nfour, PETSC_DECIDE, PETSC_DECIDE, ione, ione, PETSC_NULL_INTEGER_ARRAY, PETSC_NULL_INTEGER_ARRAY, da, ierr))
539: PetscCallA(DMSetFromOptions(da, ierr))
540: PetscCallA(DMSetUp(da, ierr))
542: PetscCallA(DMDAGetInfo(da, PETSC_NULL_INTEGER, user%mx, user%my, PETSC_NULL_INTEGER, PETSC_NULL_INTEGER, PETSC_NULL_INTEGER, PETSC_NULL_INTEGER, PETSC_NULL_INTEGER, PETSC_NULL_INTEGER, PETSC_NULL_DMBOUNDARYTYPE, PETSC_NULL_DMBOUNDARYTYPE, PETSC_NULL_DMBOUNDARYTYPE, PETSC_NULL_DMDASTENCILTYPE, ierr))
544: !
545: ! Visualize the distribution of the array across the processors
546: !
547: ! PetscCallA(DMView(da,PETSC_VIEWER_DRAW_WORLD,ierr))
549: ! Extract global and local vectors from DMDA; then duplicate for remaining
550: ! vectors that are the same types
551: PetscCallA(DMCreateGlobalVector(da, x, ierr))
552: PetscCallA(VecDuplicate(x, r, ierr))
554: ! Get local grid boundaries (for 2-dimensional DMDA)
555: PetscCallA(DMDAGetCorners(da, user%xs, user%ys, PETSC_NULL_INTEGER, user%xm, user%ym, PETSC_NULL_INTEGER, ierr))
556: PetscCallA(DMDAGetGhostCorners(da, user%gxs, user%gys, PETSC_NULL_INTEGER, user%gxm, user%gym, PETSC_NULL_INTEGER, ierr))
558: ! Here we shift the starting indices up by one so that we can easily
559: ! use the Fortran convention of 1-based indices (rather 0-based indices).
560: user%xs = user%xs + 1
561: user%ys = user%ys + 1
562: user%gxs = user%gxs + 1
563: user%gys = user%gys + 1
565: user%ye = user%ys + user%ym - 1
566: user%xe = user%xs + user%xm - 1
567: user%gye = user%gys + user%gym - 1
568: user%gxe = user%gxs + user%gxm - 1
570: PetscCallA(SNESSetApplicationContext(snes, user, ierr))
572: ! Set function evaluation routine and vector
573: PetscCallA(SNESSetFunction(snes, r, FormFunction, user, ierr))
575: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
576: ! Create matrix data structure; set Jacobian evaluation routine
577: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
579: ! Set Jacobian matrix data structure and default Jacobian evaluation
580: ! routine. User can override with:
581: ! -snes_fd : default finite differencing approximation of Jacobian
582: ! -snes_mf : matrix-free Newton-Krylov method with no preconditioning
583: ! (unless user explicitly sets preconditioner)
584: ! -snes_mf_operator : form matrix used to construct the preconditioner as set by the user,
585: ! but use matrix-free approx for Jacobian-vector
586: ! products within Newton-Krylov method
587: !
588: ! Note: For the parallel case, vectors and matrices MUST be partitioned
589: ! accordingly. When using distributed arrays (DMDAs) to create vectors,
590: ! the DMDAs determine the problem partitioning. We must explicitly
591: ! specify the local matrix dimensions upon its creation for compatibility
592: ! with the vector distribution. Thus, the generic MatCreate() routine
593: ! is NOT sufficient when working with distributed arrays.
594: !
595: ! Note: Here we only approximately preallocate storage space for the
596: ! Jacobian. See the users manual for a discussion of better techniques
597: ! for preallocating matrix memory.
599: PetscCallA(PetscOptionsHasName(PETSC_NULL_OPTIONS, PETSC_NULL_CHARACTER, '-snes_mf', matrix_free, ierr))
600: if (.not. matrix_free) then
601: PetscCallA(DMSetMatType(da, MATAIJ, ierr))
602: PetscCallA(DMCreateMatrix(da, J, ierr))
603: PetscCallA(SNESSetJacobian(snes, J, J, FormJacobian, user, ierr))
604: end if
606: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
607: ! Customize nonlinear solver; set runtime options
608: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
609: ! Set runtime options (e.g., -snes_monitor -snes_rtol <rtol> -ksp_type <type>)
610: PetscCallA(SNESSetDM(snes, da, ierr))
611: PetscCallA(SNESSetFromOptions(snes, ierr))
613: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
614: ! Evaluate initial guess; then solve nonlinear system.
615: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
616: ! Note: The user should initialize the vector, x, with the initial guess
617: ! for the nonlinear solver prior to calling SNESSolve(). In particular,
618: ! to employ an initial guess of zero, the user should explicitly set
619: ! this vector to zero by calling VecSet().
621: PetscCallA(FormInitialGuess(snes, x, ierr))
622: PetscCallA(SNESSolve(snes, PETSC_NULL_VEC, x, ierr))
623: PetscCallA(SNESGetIterationNumber(snes, its, ierr))
624: if (user%rank == 0) then
625: write (6, 100) its
626: end if
627: 100 format('Number of SNES iterations = ', i5)
629: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
630: ! Free work space. All PETSc objects should be destroyed when they
631: ! are no longer needed.
632: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
633: if (.not. matrix_free) PetscCallA(MatDestroy(J, ierr))
634: PetscCallA(VecDestroy(x, ierr))
635: PetscCallA(VecDestroy(r, ierr))
636: PetscCallA(SNESDestroy(snes, ierr))
637: PetscCallA(DMDestroy(da, ierr))
639: PetscCallA(PetscFinalize(ierr))
640: end
641: !
642: !/*TEST
643: !
644: ! test:
645: ! nsize: 4
646: ! args: -snes_mf -pc_type none -da_processors_x 4 -da_processors_y 1 -snes_monitor_short -ksp_gmres_cgs_refinement_type refine_always
647: ! requires: !single
648: !
649: ! test:
650: ! suffix: 2
651: ! nsize: 4
652: ! args: -da_processors_x 2 -da_processors_y 2 -snes_monitor_short -ksp_gmres_cgs_refinement_type refine_always
653: ! requires: !single
654: !
655: ! test:
656: ! suffix: 3
657: ! nsize: 3
658: ! args: -snes_fd -snes_monitor_short -ksp_gmres_cgs_refinement_type refine_always
659: ! requires: !single
660: !
661: ! test:
662: ! suffix: 4
663: ! nsize: 3
664: ! args: -snes_mf_operator -snes_monitor_short -ksp_gmres_cgs_refinement_type refine_always
665: ! requires: !single
666: !
667: ! test:
668: ! suffix: 5
669: ! requires: !single
670: !
671: !TEST*/