xref: /petsc/include/petscdt.h (revision 6dd63270497ad23dcf16ae500a87ff2b2a0b7474)
1 /*
2   Common tools for constructing discretizations
3 */
4 #pragma once
5 
6 #include <petscsys.h>
7 #include <petscdmtypes.h>
8 #include <petscistypes.h>
9 
10 /* MANSEC = DM */
11 /* SUBMANSEC = DT */
12 
13 PETSC_EXTERN PetscClassId PETSCQUADRATURE_CLASSID;
14 
15 /*S
16   PetscQuadrature - Quadrature rule for numerical integration.
17 
18   Level: beginner
19 
20 .seealso: `PetscQuadratureCreate()`, `PetscQuadratureDestroy()`
21 S*/
22 typedef struct _p_PetscQuadrature *PetscQuadrature;
23 
24 /*E
25   PetscGaussLobattoLegendreCreateType - algorithm used to compute the Gauss-Lobatto-Legendre nodes and weights
26 
27   Values:
28 +  `PETSCGAUSSLOBATTOLEGENDRE_VIA_LINEAR_ALGEBRA` - compute the nodes via linear algebra
29 -  `PETSCGAUSSLOBATTOLEGENDRE_VIA_NEWTON`         - compute the nodes by solving a nonlinear equation with Newton's method
30 
31   Level: intermediate
32 
33 .seealso: `PetscQuadrature`
34 E*/
35 typedef enum {
36   PETSCGAUSSLOBATTOLEGENDRE_VIA_LINEAR_ALGEBRA,
37   PETSCGAUSSLOBATTOLEGENDRE_VIA_NEWTON
38 } PetscGaussLobattoLegendreCreateType;
39 
40 /*E
41   PetscDTNodeType - A description of strategies for generating nodes (both
42   quadrature nodes and nodes for Lagrange polynomials)
43 
44   Values:
45 + `PETSCDTNODES_DEFAULT`     - Nodes chosen by PETSc
46 . `PETSCDTNODES_GAUSSJACOBI` - Nodes at either Gauss-Jacobi or Gauss-Lobatto-Jacobi quadrature points
47 . `PETSCDTNODES_EQUISPACED`  - Nodes equispaced either including the endpoints or excluding them
48 - `PETSCDTNODES_TANHSINH`    - Nodes at Tanh-Sinh quadrature points
49 
50   Level: intermediate
51 
52   Note:
53   A `PetscDTNodeType` can be paired with a `PetscBool` to indicate whether
54   the nodes include endpoints or not, and in the case of `PETSCDT_GAUSSJACOBI`
55   with exponents for the weight function.
56 
57 .seealso: `PetscQuadrature`
58 E*/
59 typedef enum {
60   PETSCDTNODES_DEFAULT     = -1,
61   PETSCDTNODES_GAUSSJACOBI = 0,
62   PETSCDTNODES_EQUISPACED  = 1,
63   PETSCDTNODES_TANHSINH    = 2
64 } PetscDTNodeType;
65 
66 PETSC_EXTERN const char *const *const PetscDTNodeTypes;
67 
68 /*E
69   PetscDTSimplexQuadratureType - A description of classes of quadrature rules for simplices
70 
71   Values:
72 +  `PETSCDTSIMPLEXQUAD_DEFAULT` - Quadrature rule chosen by PETSc
73 .  `PETSCDTSIMPLEXQUAD_CONIC`   - Quadrature rules constructed as
74                                   conically-warped tensor products of 1D
75                                   Gauss-Jacobi quadrature rules.  These are
76                                   explicitly computable in any dimension for any
77                                   degree, and the tensor-product structure can be
78                                   exploited by sum-factorization methods, but
79                                   they are not efficient in terms of nodes per
80                                   polynomial degree.
81 -  `PETSCDTSIMPLEXQUAD_MINSYM`  - Quadrature rules that are fully symmetric
82                                   (symmetries of the simplex preserve the nodes
83                                   and weights) with minimal (or near minimal)
84                                   number of nodes.  In dimensions higher than 1
85                                   these are not simple to compute, so lookup
86                                   tables are used.
87 
88   Level: intermediate
89 
90 .seealso: `PetscQuadrature`, `PetscDTSimplexQuadrature()`
91 E*/
92 typedef enum {
93   PETSCDTSIMPLEXQUAD_DEFAULT = -1,
94   PETSCDTSIMPLEXQUAD_CONIC   = 0,
95   PETSCDTSIMPLEXQUAD_MINSYM  = 1
96 } PetscDTSimplexQuadratureType;
97 
98 PETSC_EXTERN const char *const *const PetscDTSimplexQuadratureTypes;
99 
100 PETSC_EXTERN PetscErrorCode PetscQuadratureCreate(MPI_Comm, PetscQuadrature *);
101 PETSC_EXTERN PetscErrorCode PetscQuadratureDuplicate(PetscQuadrature, PetscQuadrature *);
102 PETSC_EXTERN PetscErrorCode PetscQuadratureGetCellType(PetscQuadrature, DMPolytopeType *);
103 PETSC_EXTERN PetscErrorCode PetscQuadratureSetCellType(PetscQuadrature, DMPolytopeType);
104 PETSC_EXTERN PetscErrorCode PetscQuadratureGetOrder(PetscQuadrature, PetscInt *);
105 PETSC_EXTERN PetscErrorCode PetscQuadratureSetOrder(PetscQuadrature, PetscInt);
106 PETSC_EXTERN PetscErrorCode PetscQuadratureGetNumComponents(PetscQuadrature, PetscInt *);
107 PETSC_EXTERN PetscErrorCode PetscQuadratureSetNumComponents(PetscQuadrature, PetscInt);
108 PETSC_EXTERN PetscErrorCode PetscQuadratureEqual(PetscQuadrature, PetscQuadrature, PetscBool *);
109 PETSC_EXTERN PetscErrorCode PetscQuadratureGetData(PetscQuadrature, PetscInt *, PetscInt *, PetscInt *, const PetscReal *[], const PetscReal *[]);
110 PETSC_EXTERN PetscErrorCode PetscQuadratureSetData(PetscQuadrature, PetscInt, PetscInt, PetscInt, const PetscReal[], const PetscReal[]);
111 PETSC_EXTERN PetscErrorCode PetscQuadratureView(PetscQuadrature, PetscViewer);
112 PETSC_EXTERN PetscErrorCode PetscQuadratureDestroy(PetscQuadrature *);
113 
114 PETSC_EXTERN PetscErrorCode PetscDTTensorQuadratureCreate(PetscQuadrature, PetscQuadrature, PetscQuadrature *);
115 PETSC_EXTERN PetscErrorCode PetscQuadratureExpandComposite(PetscQuadrature, PetscInt, const PetscReal[], const PetscReal[], PetscQuadrature *);
116 PETSC_EXTERN PetscErrorCode PetscQuadratureComputePermutations(PetscQuadrature, PetscInt *, IS *[]);
117 
118 PETSC_EXTERN PetscErrorCode PetscQuadraturePushForward(PetscQuadrature, PetscInt, const PetscReal[], const PetscReal[], const PetscReal[], PetscInt, PetscQuadrature *);
119 
120 PETSC_EXTERN PetscErrorCode PetscDTLegendreEval(PetscInt, const PetscReal *, PetscInt, const PetscInt *, PetscReal *, PetscReal *, PetscReal *);
121 PETSC_EXTERN PetscErrorCode PetscDTJacobiNorm(PetscReal, PetscReal, PetscInt, PetscReal *);
122 PETSC_EXTERN PetscErrorCode PetscDTJacobiEval(PetscInt, PetscReal, PetscReal, const PetscReal *, PetscInt, const PetscInt *, PetscReal *, PetscReal *, PetscReal *);
123 PETSC_EXTERN PetscErrorCode PetscDTJacobiEvalJet(PetscReal, PetscReal, PetscInt, const PetscReal[], PetscInt, PetscInt, PetscReal[]);
124 PETSC_EXTERN PetscErrorCode PetscDTPKDEvalJet(PetscInt, PetscInt, const PetscReal[], PetscInt, PetscInt, PetscReal[]);
125 PETSC_EXTERN PetscErrorCode PetscDTPTrimmedSize(PetscInt, PetscInt, PetscInt, PetscInt *);
126 PETSC_EXTERN PetscErrorCode PetscDTPTrimmedEvalJet(PetscInt, PetscInt, const PetscReal[], PetscInt, PetscInt, PetscInt, PetscReal[]);
127 PETSC_EXTERN PetscErrorCode PetscDTGaussQuadrature(PetscInt, PetscReal, PetscReal, PetscReal *, PetscReal *);
128 PETSC_EXTERN PetscErrorCode PetscDTGaussJacobiQuadrature(PetscInt, PetscReal, PetscReal, PetscReal, PetscReal, PetscReal *, PetscReal *);
129 PETSC_EXTERN PetscErrorCode PetscDTGaussLobattoJacobiQuadrature(PetscInt, PetscReal, PetscReal, PetscReal, PetscReal, PetscReal *, PetscReal *);
130 PETSC_EXTERN PetscErrorCode PetscDTGaussLobattoLegendreQuadrature(PetscInt, PetscGaussLobattoLegendreCreateType, PetscReal *, PetscReal *);
131 PETSC_EXTERN PetscErrorCode PetscDTReconstructPoly(PetscInt, PetscInt, const PetscReal *, PetscInt, const PetscReal *, PetscReal *);
132 PETSC_EXTERN PetscErrorCode PetscDTGaussTensorQuadrature(PetscInt, PetscInt, PetscInt, PetscReal, PetscReal, PetscQuadrature *);
133 PETSC_EXTERN PetscErrorCode PetscDTStroudConicalQuadrature(PetscInt, PetscInt, PetscInt, PetscReal, PetscReal, PetscQuadrature *);
134 PETSC_EXTERN PetscErrorCode PetscDTSimplexQuadrature(PetscInt, PetscInt, PetscDTSimplexQuadratureType, PetscQuadrature *);
135 PETSC_EXTERN PetscErrorCode PetscDTCreateDefaultQuadrature(DMPolytopeType, PetscInt, PetscQuadrature *, PetscQuadrature *);
136 
137 PETSC_EXTERN PetscErrorCode PetscDTTanhSinhTensorQuadrature(PetscInt, PetscInt, PetscReal, PetscReal, PetscQuadrature *);
138 PETSC_EXTERN PetscErrorCode PetscDTTanhSinhIntegrate(void (*)(const PetscReal[], void *, PetscReal *), PetscReal, PetscReal, PetscInt, void *, PetscReal *);
139 PETSC_EXTERN PetscErrorCode PetscDTTanhSinhIntegrateMPFR(void (*)(const PetscReal[], void *, PetscReal *), PetscReal, PetscReal, PetscInt, void *, PetscReal *);
140 
141 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreIntegrate(PetscInt, PetscReal *, PetscReal *, const PetscReal *, PetscReal *);
142 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementLaplacianCreate(PetscInt, PetscReal *, PetscReal *, PetscReal ***);
143 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementLaplacianDestroy(PetscInt, PetscReal *, PetscReal *, PetscReal ***);
144 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementGradientCreate(PetscInt, PetscReal *, PetscReal *, PetscReal ***, PetscReal ***);
145 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementGradientDestroy(PetscInt, PetscReal *, PetscReal *, PetscReal ***, PetscReal ***);
146 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementAdvectionCreate(PetscInt, PetscReal *, PetscReal *, PetscReal ***);
147 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementAdvectionDestroy(PetscInt, PetscReal *, PetscReal *, PetscReal ***);
148 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementMassCreate(PetscInt, PetscReal *, PetscReal *, PetscReal ***);
149 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementMassDestroy(PetscInt, PetscReal *, PetscReal *, PetscReal ***);
150 
151 /*MC
152   PETSC_FORM_DEGREE_UNDEFINED - Indicates that a field does not have
153   a well-defined form degree in exterior calculus.
154 
155   Level: advanced
156 
157 .seealso: `PetscDTAltV`, `PetscDualSpaceGetFormDegree()`
158 M*/
159 #define PETSC_FORM_DEGREE_UNDEFINED PETSC_INT_MIN
160 
161 PETSC_EXTERN PetscErrorCode PetscDTAltVApply(PetscInt, PetscInt, const PetscReal *, const PetscReal *, PetscReal *);
162 PETSC_EXTERN PetscErrorCode PetscDTAltVWedge(PetscInt, PetscInt, PetscInt, const PetscReal *, const PetscReal *, PetscReal *);
163 PETSC_EXTERN PetscErrorCode PetscDTAltVWedgeMatrix(PetscInt, PetscInt, PetscInt, const PetscReal *, PetscReal *);
164 PETSC_EXTERN PetscErrorCode PetscDTAltVPullback(PetscInt, PetscInt, const PetscReal *, PetscInt, const PetscReal *, PetscReal *);
165 PETSC_EXTERN PetscErrorCode PetscDTAltVPullbackMatrix(PetscInt, PetscInt, const PetscReal *, PetscInt, PetscReal *);
166 PETSC_EXTERN PetscErrorCode PetscDTAltVInterior(PetscInt, PetscInt, const PetscReal *, const PetscReal *, PetscReal *);
167 PETSC_EXTERN PetscErrorCode PetscDTAltVInteriorMatrix(PetscInt, PetscInt, const PetscReal *, PetscReal *);
168 PETSC_EXTERN PetscErrorCode PetscDTAltVInteriorPattern(PetscInt, PetscInt, PetscInt (*)[3]);
169 PETSC_EXTERN PetscErrorCode PetscDTAltVStar(PetscInt, PetscInt, PetscInt, const PetscReal *, PetscReal *);
170 
171 PETSC_EXTERN PetscErrorCode PetscDTBaryToIndex(PetscInt, PetscInt, const PetscInt[], PetscInt *);
172 PETSC_EXTERN PetscErrorCode PetscDTIndexToBary(PetscInt, PetscInt, PetscInt, PetscInt[]);
173 PETSC_EXTERN PetscErrorCode PetscDTGradedOrderToIndex(PetscInt, const PetscInt[], PetscInt *);
174 PETSC_EXTERN PetscErrorCode PetscDTIndexToGradedOrder(PetscInt, PetscInt, PetscInt[]);
175 
176 #if defined(PETSC_USE_64BIT_INDICES)
177   #define PETSC_FACTORIAL_MAX 20
178   #define PETSC_BINOMIAL_MAX  61
179 #else
180   #define PETSC_FACTORIAL_MAX 12
181   #define PETSC_BINOMIAL_MAX  29
182 #endif
183 
184 /*MC
185    PetscDTFactorial - Approximate n! as a real number
186 
187    Input Parameter:
188 .  n - a non-negative integer
189 
190    Output Parameter:
191 .  factorial - n!
192 
193    Level: beginner
194 
195 .seealso: `PetscDTFactorialInt()`, `PetscDTBinomialInt()`, `PetscDTBinomial()`
196 M*/
197 static inline PetscErrorCode PetscDTFactorial(PetscInt n, PetscReal *factorial)
198 {
199   PetscReal f = 1.0;
200 
201   PetscFunctionBegin;
202   *factorial = -1.0;
203   PetscCheck(n >= 0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Factorial called with negative number %" PetscInt_FMT, n);
204   for (PetscInt i = 1; i < n + 1; ++i) f *= (PetscReal)i;
205   *factorial = f;
206   PetscFunctionReturn(PETSC_SUCCESS);
207 }
208 
209 /*MC
210    PetscDTFactorialInt - Compute n! as an integer
211 
212    Input Parameter:
213 .  n - a non-negative integer
214 
215    Output Parameter:
216 .  factorial - n!
217 
218    Level: beginner
219 
220    Note:
221    This is limited to `n` such that n! can be represented by `PetscInt`, which is 12 if `PetscInt` is a signed 32-bit integer and 20 if `PetscInt` is a signed 64-bit integer.
222 
223 .seealso: `PetscDTFactorial()`, `PetscDTBinomialInt()`, `PetscDTBinomial()`
224 M*/
225 static inline PetscErrorCode PetscDTFactorialInt(PetscInt n, PetscInt *factorial)
226 {
227   PetscInt facLookup[13] = {1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 3628800, 39916800, 479001600};
228 
229   PetscFunctionBegin;
230   *factorial = -1;
231   PetscCheck(n >= 0 && n <= PETSC_FACTORIAL_MAX, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Number of elements %" PetscInt_FMT " is not in supported range [0,%d]", n, PETSC_FACTORIAL_MAX);
232   if (n <= 12) {
233     *factorial = facLookup[n];
234   } else {
235     PetscInt f = facLookup[12];
236     PetscInt i;
237 
238     for (i = 13; i < n + 1; ++i) f *= i;
239     *factorial = f;
240   }
241   PetscFunctionReturn(PETSC_SUCCESS);
242 }
243 
244 /*MC
245    PetscDTBinomial - Approximate the binomial coefficient `n` choose `k`
246 
247    Input Parameters:
248 +  n - a non-negative integer
249 -  k - an integer between 0 and `n`, inclusive
250 
251    Output Parameter:
252 .  binomial - approximation of the binomial coefficient `n` choose `k`
253 
254    Level: beginner
255 
256 .seealso: `PetscDTFactorial()`, `PetscDTFactorialInt()`, `PetscDTBinomialInt()`, `PetscDTEnumPerm()`
257 M*/
258 static inline PetscErrorCode PetscDTBinomial(PetscInt n, PetscInt k, PetscReal *binomial)
259 {
260   PetscFunctionBeginHot;
261   *binomial = -1.0;
262   PetscCheck(n >= 0 && k >= 0 && k <= n, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Binomial arguments (%" PetscInt_FMT " %" PetscInt_FMT ") must be non-negative, k <= n", n, k);
263   if (n <= 3) {
264     PetscInt binomLookup[4][4] = {
265       {1, 0, 0, 0},
266       {1, 1, 0, 0},
267       {1, 2, 1, 0},
268       {1, 3, 3, 1}
269     };
270 
271     *binomial = (PetscReal)binomLookup[n][k];
272   } else {
273     PetscReal binom = 1.0;
274 
275     k = PetscMin(k, n - k);
276     for (PetscInt i = 0; i < k; i++) binom = (binom * (PetscReal)(n - i)) / (PetscReal)(i + 1);
277     *binomial = binom;
278   }
279   PetscFunctionReturn(PETSC_SUCCESS);
280 }
281 
282 /*MC
283    PetscDTBinomialInt - Compute the binomial coefficient `n` choose `k`
284 
285    Input Parameters:
286 +  n - a non-negative integer
287 -  k - an integer between 0 and `n`, inclusive
288 
289    Output Parameter:
290 .  binomial - the binomial coefficient `n` choose `k`
291 
292    Level: beginner
293 
294    Note:
295    This is limited by integers that can be represented by `PetscInt`.
296 
297    Use `PetscDTBinomial()` for real number approximations of larger values
298 
299 .seealso: `PetscDTFactorial()`, `PetscDTFactorialInt()`, `PetscDTBinomial()`, `PetscDTEnumPerm()`
300 M*/
301 static inline PetscErrorCode PetscDTBinomialInt(PetscInt n, PetscInt k, PetscInt *binomial)
302 {
303   PetscInt bin;
304 
305   PetscFunctionBegin;
306   *binomial = -1;
307   PetscCheck(n >= 0 && k >= 0 && k <= n, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Binomial arguments (%" PetscInt_FMT " %" PetscInt_FMT ") must be non-negative, k <= n", n, k);
308   PetscCheck(n <= PETSC_BINOMIAL_MAX, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Binomial elements %" PetscInt_FMT " is larger than max for PetscInt, %d", n, PETSC_BINOMIAL_MAX);
309   if (n <= 3) {
310     PetscInt binomLookup[4][4] = {
311       {1, 0, 0, 0},
312       {1, 1, 0, 0},
313       {1, 2, 1, 0},
314       {1, 3, 3, 1}
315     };
316 
317     bin = binomLookup[n][k];
318   } else {
319     PetscInt binom = 1;
320 
321     k = PetscMin(k, n - k);
322     for (PetscInt i = 0; i < k; i++) binom = (binom * (n - i)) / (i + 1);
323     bin = binom;
324   }
325   *binomial = bin;
326   PetscFunctionReturn(PETSC_SUCCESS);
327 }
328 
329 /* the following inline routines should be not be inline routines and then Fortran binding can be built automatically */
330 #define PeOp
331 
332 /*MC
333    PetscDTEnumPerm - Get a permutation of `n` integers from its encoding into the integers [0, n!) as a sequence of swaps.
334 
335    Input Parameters:
336 +  n - a non-negative integer (see note about limits below)
337 -  k - an integer in [0, n!)
338 
339    Output Parameters:
340 +  perm  - the permuted list of the integers [0, ..., n-1]
341 -  isOdd - if not `NULL`, returns whether the permutation used an even or odd number of swaps.
342 
343    Level: intermediate
344 
345    Notes:
346    A permutation can be described by the operations that convert the lists [0, 1, ..., n-1] into the permutation,
347    by a sequence of swaps, where the ith step swaps whatever number is in ith position with a number that is in
348    some position j >= i.  This swap is encoded as the difference (j - i).  The difference d_i at step i is less than
349    (n - i).  This sequence of n-1 differences [d_0, ..., d_{n-2}] is encoded as the number
350    (n-1)! * d_0 + (n-2)! * d_1 + ... + 1! * d_{n-2}.
351 
352    Limited to `n` such that `n`! can be represented by `PetscInt`, which is 12 if `PetscInt` is a signed 32-bit integer and 20 if `PetscInt` is a signed 64-bit integer.
353 
354 .seealso: `PetscDTFactorial()`, `PetscDTFactorialInt()`, `PetscDTBinomial()`, `PetscDTBinomialInt()`, `PetscDTPermIndex()`
355 M*/
356 static inline PetscErrorCode PetscDTEnumPerm(PetscInt n, PetscInt k, PetscInt *perm, PeOp PetscBool *isOdd)
357 {
358   PetscInt  odd = 0;
359   PetscInt  i;
360   PetscInt  work[PETSC_FACTORIAL_MAX];
361   PetscInt *w;
362 
363   PetscFunctionBegin;
364   if (isOdd) *isOdd = PETSC_FALSE;
365   PetscCheck(n >= 0 && n <= PETSC_FACTORIAL_MAX, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Number of elements %" PetscInt_FMT " is not in supported range [0,%d]", n, PETSC_FACTORIAL_MAX);
366   if (n >= 2) {
367     w = &work[n - 2];
368     for (i = 2; i <= n; i++) {
369       *(w--) = k % i;
370       k /= i;
371     }
372   }
373   for (i = 0; i < n; i++) perm[i] = i;
374   for (i = 0; i < n - 1; i++) {
375     PetscInt s    = work[i];
376     PetscInt swap = perm[i];
377 
378     perm[i]     = perm[i + s];
379     perm[i + s] = swap;
380     odd ^= (!!s);
381   }
382   if (isOdd) *isOdd = odd ? PETSC_TRUE : PETSC_FALSE;
383   PetscFunctionReturn(PETSC_SUCCESS);
384 }
385 
386 /*MC
387    PetscDTPermIndex - Encode a permutation of n into an integer in [0, n!).  This inverts `PetscDTEnumPerm()`.
388 
389    Input Parameters:
390 +  n    - a non-negative integer (see note about limits below)
391 -  perm - the permuted list of the integers [0, ..., n-1]
392 
393    Output Parameters:
394 +  k     - an integer in [0, n!)
395 -  isOdd - if not `NULL`, returns whether the permutation used an even or odd number of swaps.
396 
397    Level: beginner
398 
399    Note:
400    Limited to `n` such that `n`! can be represented by `PetscInt`, which is 12 if `PetscInt` is a signed 32-bit integer and 20 if `PetscInt` is a signed 64-bit integer.
401 
402 .seealso: `PetscDTFactorial()`, `PetscDTFactorialInt()`, `PetscDTBinomial()`, `PetscDTBinomialInt()`, `PetscDTEnumPerm()`
403 M*/
404 static inline PetscErrorCode PetscDTPermIndex(PetscInt n, const PetscInt *perm, PetscInt *k, PeOp PetscBool *isOdd)
405 {
406   PetscInt odd = 0;
407   PetscInt i, idx;
408   PetscInt work[PETSC_FACTORIAL_MAX];
409   PetscInt iwork[PETSC_FACTORIAL_MAX];
410 
411   PetscFunctionBeginHot;
412   *k = -1;
413   if (isOdd) *isOdd = PETSC_FALSE;
414   PetscCheck(n >= 0 && n <= PETSC_FACTORIAL_MAX, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Number of elements %" PetscInt_FMT " is not in supported range [0,%d]", n, PETSC_FACTORIAL_MAX);
415   for (i = 0; i < n; i++) work[i] = i;  /* partial permutation */
416   for (i = 0; i < n; i++) iwork[i] = i; /* partial permutation inverse */
417   for (idx = 0, i = 0; i < n - 1; i++) {
418     PetscInt j    = perm[i];
419     PetscInt icur = work[i];
420     PetscInt jloc = iwork[j];
421     PetscInt diff = jloc - i;
422 
423     idx = idx * (n - i) + diff;
424     /* swap (i, jloc) */
425     work[i]     = j;
426     work[jloc]  = icur;
427     iwork[j]    = i;
428     iwork[icur] = jloc;
429     odd ^= (!!diff);
430   }
431   *k = idx;
432   if (isOdd) *isOdd = odd ? PETSC_TRUE : PETSC_FALSE;
433   PetscFunctionReturn(PETSC_SUCCESS);
434 }
435 
436 /*MC
437    PetscDTEnumSubset - Get an ordered subset of the integers [0, ..., n - 1] from its encoding as an integers in [0, n choose k).
438    The encoding is in lexicographic order.
439 
440    Input Parameters:
441 +  n - a non-negative integer (see note about limits below)
442 .  k - an integer in [0, n]
443 -  j - an index in [0, n choose k)
444 
445    Output Parameter:
446 .  subset - the jth subset of size k of the integers [0, ..., n - 1]
447 
448    Level: beginner
449 
450    Note:
451    Limited by arguments such that `n` choose `k` can be represented by `PetscInt`
452 
453 .seealso: `PetscDTSubsetIndex()`, `PetscDTFactorial()`, `PetscDTFactorialInt()`, `PetscDTBinomial()`, `PetscDTBinomialInt()`, `PetscDTEnumPerm()`, `PetscDTPermIndex()`
454 M*/
455 static inline PetscErrorCode PetscDTEnumSubset(PetscInt n, PetscInt k, PetscInt j, PetscInt *subset)
456 {
457   PetscInt Nk;
458 
459   PetscFunctionBeginHot;
460   PetscCall(PetscDTBinomialInt(n, k, &Nk));
461   for (PetscInt i = 0, l = 0; i < n && l < k; i++) {
462     PetscInt Nminuskminus = (Nk * (k - l)) / (n - i);
463     PetscInt Nminusk      = Nk - Nminuskminus;
464 
465     if (j < Nminuskminus) {
466       subset[l++] = i;
467       Nk          = Nminuskminus;
468     } else {
469       j -= Nminuskminus;
470       Nk = Nminusk;
471     }
472   }
473   PetscFunctionReturn(PETSC_SUCCESS);
474 }
475 
476 /*MC
477    PetscDTSubsetIndex - Convert an ordered subset of k integers from the set [0, ..., n - 1] to its encoding as an integers in [0, n choose k) in lexicographic order.
478    This is the inverse of `PetscDTEnumSubset`.
479 
480    Input Parameters:
481 +  n      - a non-negative integer (see note about limits below)
482 .  k      - an integer in [0, n]
483 -  subset - an ordered subset of the integers [0, ..., n - 1]
484 
485    Output Parameter:
486 .  index - the rank of the subset in lexicographic order
487 
488    Level: beginner
489 
490    Note:
491    Limited by arguments such that `n` choose `k` can be represented by `PetscInt`
492 
493 .seealso: `PetscDTEnumSubset()`, `PetscDTFactorial()`, `PetscDTFactorialInt()`, `PetscDTBinomial()`, `PetscDTBinomialInt()`, `PetscDTEnumPerm()`, `PetscDTPermIndex()`
494 M*/
495 static inline PetscErrorCode PetscDTSubsetIndex(PetscInt n, PetscInt k, const PetscInt *subset, PetscInt *index)
496 {
497   PetscInt j = 0, Nk;
498 
499   PetscFunctionBegin;
500   *index = -1;
501   PetscCall(PetscDTBinomialInt(n, k, &Nk));
502   for (PetscInt i = 0, l = 0; i < n && l < k; i++) {
503     PetscInt Nminuskminus = (Nk * (k - l)) / (n - i);
504     PetscInt Nminusk      = Nk - Nminuskminus;
505 
506     if (subset[l] == i) {
507       l++;
508       Nk = Nminuskminus;
509     } else {
510       j += Nminuskminus;
511       Nk = Nminusk;
512     }
513   }
514   *index = j;
515   PetscFunctionReturn(PETSC_SUCCESS);
516 }
517 
518 /*MC
519    PetscDTEnumSplit - Split the integers [0, ..., n - 1] into two complementary ordered subsets, the first subset of size k and being the jth subset of that size in lexicographic order.
520 
521    Input Parameters:
522 +  n - a non-negative integer (see note about limits below)
523 .  k - an integer in [0, n]
524 -  j - an index in [0, n choose k)
525 
526    Output Parameters:
527 +  perm  - the jth subset of size k of the integers [0, ..., n - 1], followed by its complementary set.
528 -  isOdd - if not `NULL`, return whether perm is an even or odd permutation.
529 
530    Level: beginner
531 
532    Note:
533    Limited by arguments such that `n` choose `k` can be represented by `PetscInt`
534 
535 .seealso: `PetscDTEnumSubset()`, `PetscDTSubsetIndex()`, `PetscDTFactorial()`, `PetscDTFactorialInt()`, `PetscDTBinomial()`, `PetscDTBinomialInt()`, `PetscDTEnumPerm()`,
536           `PetscDTPermIndex()`
537 M*/
538 static inline PetscErrorCode PetscDTEnumSplit(PetscInt n, PetscInt k, PetscInt j, PetscInt *perm, PeOp PetscBool *isOdd)
539 {
540   PetscInt  i, l, m, Nk, odd = 0;
541   PetscInt *subcomp = PetscSafePointerPlusOffset(perm, k);
542 
543   PetscFunctionBegin;
544   if (isOdd) *isOdd = PETSC_FALSE;
545   PetscCall(PetscDTBinomialInt(n, k, &Nk));
546   for (i = 0, l = 0, m = 0; i < n && l < k; i++) {
547     PetscInt Nminuskminus = (Nk * (k - l)) / (n - i);
548     PetscInt Nminusk      = Nk - Nminuskminus;
549 
550     if (j < Nminuskminus) {
551       perm[l++] = i;
552       Nk        = Nminuskminus;
553     } else {
554       subcomp[m++] = i;
555       j -= Nminuskminus;
556       odd ^= ((k - l) & 1);
557       Nk = Nminusk;
558     }
559   }
560   for (; i < n; i++) subcomp[m++] = i;
561   if (isOdd) *isOdd = odd ? PETSC_TRUE : PETSC_FALSE;
562   PetscFunctionReturn(PETSC_SUCCESS);
563 }
564 
565 struct _n_PetscTabulation {
566   PetscInt    K;    /* Indicates a k-jet, namely tabulated derivatives up to order k */
567   PetscInt    Nr;   /* The number of tabulation replicas (often 1) */
568   PetscInt    Np;   /* The number of tabulation points in a replica */
569   PetscInt    Nb;   /* The number of functions tabulated */
570   PetscInt    Nc;   /* The number of function components */
571   PetscInt    cdim; /* The coordinate dimension */
572   PetscReal **T;    /* The tabulation T[K] of functions and their derivatives
573                        T[0] = B[Nr*Np][Nb][Nc]:             The basis function values at quadrature points
574                        T[1] = D[Nr*Np][Nb][Nc][cdim]:       The basis function derivatives at quadrature points
575                        T[2] = H[Nr*Np][Nb][Nc][cdim][cdim]: The basis function second derivatives at quadrature points */
576 };
577 
578 /*S
579    PetscTabulation - PETSc object that manages tabulations for finite element methods.
580 
581    Level: intermediate
582 
583    Note:
584    This is a pointer to a C struct, hence the data in it may be accessed directly.
585 
586    Fortran Note:
587    Use `PetscTabulationGetData()` and `PetscTabulationRestoreData()` to access the arrays in the tabulation.
588 
589    Developer Note:
590    TODO: put the meaning of the struct fields in this manual page
591 
592 .seealso: `PetscTabulationDestroy()`, `PetscFECreateTabulation()`, `PetscFEGetCellTabulation()`
593 S*/
594 typedef struct _n_PetscTabulation *PetscTabulation;
595 
596 typedef PetscErrorCode (*PetscProbFunc)(const PetscReal[], const PetscReal[], PetscReal[]);
597 
598 typedef enum {
599   DTPROB_DENSITY_CONSTANT,
600   DTPROB_DENSITY_GAUSSIAN,
601   DTPROB_DENSITY_MAXWELL_BOLTZMANN,
602   DTPROB_NUM_DENSITY
603 } DTProbDensityType;
604 PETSC_EXTERN const char *const DTProbDensityTypes[];
605 
606 PETSC_EXTERN PetscErrorCode PetscPDFMaxwellBoltzmann1D(const PetscReal[], const PetscReal[], PetscReal[]);
607 PETSC_EXTERN PetscErrorCode PetscCDFMaxwellBoltzmann1D(const PetscReal[], const PetscReal[], PetscReal[]);
608 PETSC_EXTERN PetscErrorCode PetscPDFMaxwellBoltzmann2D(const PetscReal[], const PetscReal[], PetscReal[]);
609 PETSC_EXTERN PetscErrorCode PetscCDFMaxwellBoltzmann2D(const PetscReal[], const PetscReal[], PetscReal[]);
610 PETSC_EXTERN PetscErrorCode PetscPDFMaxwellBoltzmann3D(const PetscReal[], const PetscReal[], PetscReal[]);
611 PETSC_EXTERN PetscErrorCode PetscCDFMaxwellBoltzmann3D(const PetscReal[], const PetscReal[], PetscReal[]);
612 PETSC_EXTERN PetscErrorCode PetscPDFGaussian1D(const PetscReal[], const PetscReal[], PetscReal[]);
613 PETSC_EXTERN PetscErrorCode PetscCDFGaussian1D(const PetscReal[], const PetscReal[], PetscReal[]);
614 PETSC_EXTERN PetscErrorCode PetscPDFSampleGaussian1D(const PetscReal[], const PetscReal[], PetscReal[]);
615 PETSC_EXTERN PetscErrorCode PetscPDFGaussian2D(const PetscReal[], const PetscReal[], PetscReal[]);
616 PETSC_EXTERN PetscErrorCode PetscPDFSampleGaussian2D(const PetscReal[], const PetscReal[], PetscReal[]);
617 PETSC_EXTERN PetscErrorCode PetscPDFGaussian3D(const PetscReal[], const PetscReal[], PetscReal[]);
618 PETSC_EXTERN PetscErrorCode PetscPDFSampleGaussian3D(const PetscReal[], const PetscReal[], PetscReal[]);
619 PETSC_EXTERN PetscErrorCode PetscPDFConstant1D(const PetscReal[], const PetscReal[], PetscReal[]);
620 PETSC_EXTERN PetscErrorCode PetscCDFConstant1D(const PetscReal[], const PetscReal[], PetscReal[]);
621 PETSC_EXTERN PetscErrorCode PetscPDFSampleConstant1D(const PetscReal[], const PetscReal[], PetscReal[]);
622 PETSC_EXTERN PetscErrorCode PetscPDFConstant2D(const PetscReal[], const PetscReal[], PetscReal[]);
623 PETSC_EXTERN PetscErrorCode PetscCDFConstant2D(const PetscReal[], const PetscReal[], PetscReal[]);
624 PETSC_EXTERN PetscErrorCode PetscPDFSampleConstant2D(const PetscReal[], const PetscReal[], PetscReal[]);
625 PETSC_EXTERN PetscErrorCode PetscPDFConstant3D(const PetscReal[], const PetscReal[], PetscReal[]);
626 PETSC_EXTERN PetscErrorCode PetscCDFConstant3D(const PetscReal[], const PetscReal[], PetscReal[]);
627 PETSC_EXTERN PetscErrorCode PetscPDFSampleConstant3D(const PetscReal[], const PetscReal[], PetscReal[]);
628 PETSC_EXTERN PetscErrorCode PetscProbCreateFromOptions(PetscInt, const char[], const char[], PetscProbFunc *, PetscProbFunc *, PetscProbFunc *);
629 
630 #include <petscvec.h>
631 
632 PETSC_EXTERN PetscErrorCode PetscProbComputeKSStatistic(Vec, PetscProbFunc, PetscReal *);
633 PETSC_EXTERN PetscErrorCode PetscProbComputeKSStatisticWeighted(Vec, Vec, PetscProbFunc, PetscReal *);
634 PETSC_EXTERN PetscErrorCode PetscProbComputeKSStatisticMagnitude(Vec, PetscProbFunc, PetscReal *);
635