xref: /petsc/include/petscdt.h (revision d3ef4daaf99d19e98efa749367c59a1afaa53b93)
1 /*
2   Common tools for constructing discretizations
3 */
4 #if !defined(PETSCDT_H)
5 #define PETSCDT_H
6 
7 #include <petscsys.h>
8 
9 /* SUBMANSEC = DT */
10 
11 PETSC_EXTERN PetscClassId PETSCQUADRATURE_CLASSID;
12 
13 /*S
14   PetscQuadrature - Quadrature rule for integration.
15 
16   Level: beginner
17 
18 .seealso: `PetscQuadratureCreate()`, `PetscQuadratureDestroy()`
19 S*/
20 typedef struct _p_PetscQuadrature *PetscQuadrature;
21 
22 /*E
23   PetscGaussLobattoLegendreCreateType - algorithm used to compute the Gauss-Lobatto-Legendre nodes and weights
24 
25   Level: intermediate
26 
27 $  PETSCGAUSSLOBATTOLEGENDRE_VIA_LINEAR_ALGEBRA - compute the nodes via linear algebra
28 $  PETSCGAUSSLOBATTOLEGENDRE_VIA_NEWTON - compute the nodes by solving a nonlinear equation with Newton's method
29 
30 E*/
31 typedef enum {PETSCGAUSSLOBATTOLEGENDRE_VIA_LINEAR_ALGEBRA,PETSCGAUSSLOBATTOLEGENDRE_VIA_NEWTON} PetscGaussLobattoLegendreCreateType;
32 
33 /*E
34   PetscDTNodeType - A description of strategies for generating nodes (both
35   quadrature nodes and nodes for Lagrange polynomials)
36 
37   Level: intermediate
38 
39 $  PETSCDTNODES_DEFAULT - Nodes chosen by PETSc
40 $  PETSCDTNODES_GAUSSJACOBI - Nodes at either Gauss-Jacobi or Gauss-Lobatto-Jacobi quadrature points
41 $  PETSCDTNODES_EQUISPACED - Nodes equispaced either including the endpoints or excluding them
42 $  PETSCDTNODES_TANHSINH - Nodes at Tanh-Sinh quadrature points
43 
44   Note: a PetscDTNodeType can be paired with a PetscBool to indicate whether
45   the nodes include endpoints or not, and in the case of PETSCDT_GAUSSJACOBI
46   with exponents for the weight function.
47 
48 E*/
49 typedef enum {PETSCDTNODES_DEFAULT=-1, PETSCDTNODES_GAUSSJACOBI, PETSCDTNODES_EQUISPACED, PETSCDTNODES_TANHSINH} PetscDTNodeType;
50 
51 PETSC_EXTERN const char *const*const PetscDTNodeTypes;
52 
53 /*E
54   PetscDTSimplexQuadratureType - A description of classes of quadrature rules for simplices
55 
56   Level: intermediate
57 
58 $  PETSCDTSIMPLEXQUAD_DEFAULT - Quadrature rule chosen by PETSc
59 $  PETSCDTSIMPLEXQUAD_CONIC   - Quadrature rules constructed as
60                                 conically-warped tensor products of 1D
61                                 Gauss-Jacobi quadrature rules.  These are
62                                 explicitly computable in any dimension for any
63                                 degree, and the tensor-product structure can be
64                                 exploited by sum-factorization methods, but
65                                 they are not efficient in terms of nodes per
66                                 polynomial degree.
67 $  PETSCDTSIMPLEXQUAD_MINSYM  - Quadrature rules that are fully symmetric
68                                 (symmetries of the simplex preserve the nodes
69                                 and weights) with minimal (or near minimal)
70                                 number of nodes.  In dimensions higher than 1
71                                 these are not simple to compute, so lookup
72                                 tables are used.
73 
74 .seealso: `PetscDTSimplexQuadrature()`
75 E*/
76 typedef enum {PETSCDTSIMPLEXQUAD_DEFAULT=-1, PETSCDTSIMPLEXQUAD_CONIC=0, PETSCDTSIMPLEXQUAD_MINSYM} PetscDTSimplexQuadratureType;
77 
78 PETSC_EXTERN const char *const*const PetscDTSimplexQuadratureTypes;
79 
80 PETSC_EXTERN PetscErrorCode PetscQuadratureCreate(MPI_Comm, PetscQuadrature *);
81 PETSC_EXTERN PetscErrorCode PetscQuadratureDuplicate(PetscQuadrature, PetscQuadrature *);
82 PETSC_EXTERN PetscErrorCode PetscQuadratureGetOrder(PetscQuadrature, PetscInt*);
83 PETSC_EXTERN PetscErrorCode PetscQuadratureSetOrder(PetscQuadrature, PetscInt);
84 PETSC_EXTERN PetscErrorCode PetscQuadratureGetNumComponents(PetscQuadrature, PetscInt*);
85 PETSC_EXTERN PetscErrorCode PetscQuadratureSetNumComponents(PetscQuadrature, PetscInt);
86 PETSC_EXTERN PetscErrorCode PetscQuadratureEqual(PetscQuadrature, PetscQuadrature, PetscBool*);
87 PETSC_EXTERN PetscErrorCode PetscQuadratureGetData(PetscQuadrature, PetscInt*, PetscInt*, PetscInt*, const PetscReal *[], const PetscReal *[]);
88 PETSC_EXTERN PetscErrorCode PetscQuadratureSetData(PetscQuadrature, PetscInt, PetscInt, PetscInt, const PetscReal [], const PetscReal []);
89 PETSC_EXTERN PetscErrorCode PetscQuadratureView(PetscQuadrature, PetscViewer);
90 PETSC_EXTERN PetscErrorCode PetscQuadratureDestroy(PetscQuadrature *);
91 
92 PETSC_EXTERN PetscErrorCode PetscDTTensorQuadratureCreate(PetscQuadrature, PetscQuadrature, PetscQuadrature *);
93 PETSC_EXTERN PetscErrorCode PetscQuadratureExpandComposite(PetscQuadrature, PetscInt, const PetscReal[], const PetscReal[], PetscQuadrature *);
94 
95 PETSC_EXTERN PetscErrorCode PetscQuadraturePushForward(PetscQuadrature, PetscInt, const PetscReal[], const PetscReal[], const PetscReal[], PetscInt, PetscQuadrature *);
96 
97 PETSC_EXTERN PetscErrorCode PetscDTLegendreEval(PetscInt,const PetscReal*,PetscInt,const PetscInt*,PetscReal*,PetscReal*,PetscReal*);
98 PETSC_EXTERN PetscErrorCode PetscDTJacobiNorm(PetscReal,PetscReal,PetscInt,PetscReal *);
99 PETSC_EXTERN PetscErrorCode PetscDTJacobiEval(PetscInt,PetscReal,PetscReal,const PetscReal*,PetscInt,const PetscInt*,PetscReal*,PetscReal*,PetscReal*);
100 PETSC_EXTERN PetscErrorCode PetscDTJacobiEvalJet(PetscReal,PetscReal,PetscInt,const PetscReal[],PetscInt,PetscInt,PetscReal[]);
101 PETSC_EXTERN PetscErrorCode PetscDTPKDEvalJet(PetscInt,PetscInt,const PetscReal[],PetscInt,PetscInt,PetscReal[]);
102 PETSC_EXTERN PetscErrorCode PetscDTPTrimmedSize(PetscInt,PetscInt,PetscInt,PetscInt*);
103 PETSC_EXTERN PetscErrorCode PetscDTPTrimmedEvalJet(PetscInt,PetscInt,const PetscReal[],PetscInt,PetscInt,PetscInt,PetscReal[]);
104 PETSC_EXTERN PetscErrorCode PetscDTGaussQuadrature(PetscInt,PetscReal,PetscReal,PetscReal*,PetscReal*);
105 PETSC_EXTERN PetscErrorCode PetscDTGaussJacobiQuadrature(PetscInt,PetscReal,PetscReal,PetscReal,PetscReal,PetscReal*,PetscReal*);
106 PETSC_EXTERN PetscErrorCode PetscDTGaussLobattoJacobiQuadrature(PetscInt,PetscReal,PetscReal,PetscReal,PetscReal,PetscReal*,PetscReal*);
107 PETSC_EXTERN PetscErrorCode PetscDTGaussLobattoLegendreQuadrature(PetscInt,PetscGaussLobattoLegendreCreateType,PetscReal*,PetscReal*);
108 PETSC_EXTERN PetscErrorCode PetscDTReconstructPoly(PetscInt,PetscInt,const PetscReal*,PetscInt,const PetscReal*,PetscReal*);
109 PETSC_EXTERN PetscErrorCode PetscDTGaussTensorQuadrature(PetscInt,PetscInt,PetscInt,PetscReal,PetscReal,PetscQuadrature*);
110 PETSC_EXTERN PetscErrorCode PetscDTStroudConicalQuadrature(PetscInt,PetscInt,PetscInt,PetscReal,PetscReal,PetscQuadrature*);
111 PETSC_EXTERN PetscErrorCode PetscDTSimplexQuadrature(PetscInt,PetscInt,PetscDTSimplexQuadratureType,PetscQuadrature*);
112 
113 PETSC_EXTERN PetscErrorCode PetscDTTanhSinhTensorQuadrature(PetscInt, PetscInt, PetscReal, PetscReal, PetscQuadrature *);
114 PETSC_EXTERN PetscErrorCode PetscDTTanhSinhIntegrate(void (*)(const PetscReal[], void *, PetscReal *), PetscReal, PetscReal, PetscInt, void *, PetscReal *);
115 PETSC_EXTERN PetscErrorCode PetscDTTanhSinhIntegrateMPFR(void (*)(const PetscReal[], void *, PetscReal *), PetscReal, PetscReal, PetscInt, void *, PetscReal *);
116 
117 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreIntegrate(PetscInt, PetscReal *, PetscReal *, const PetscReal *, PetscReal *);
118 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementLaplacianCreate(PetscInt, PetscReal *, PetscReal *, PetscReal ***);
119 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementLaplacianDestroy(PetscInt, PetscReal *, PetscReal *, PetscReal ***);
120 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementGradientCreate(PetscInt, PetscReal *, PetscReal *, PetscReal ***, PetscReal ***);
121 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementGradientDestroy(PetscInt, PetscReal *, PetscReal *, PetscReal ***, PetscReal ***);
122 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementAdvectionCreate(PetscInt, PetscReal *, PetscReal *, PetscReal ***);
123 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementAdvectionDestroy(PetscInt, PetscReal *, PetscReal *, PetscReal ***);
124 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementMassCreate(PetscInt, PetscReal *, PetscReal *, PetscReal ***);
125 PETSC_EXTERN PetscErrorCode PetscGaussLobattoLegendreElementMassDestroy(PetscInt, PetscReal *, PetscReal *, PetscReal ***);
126 
127 PETSC_EXTERN PetscErrorCode PetscDTAltVApply(PetscInt, PetscInt, const PetscReal *, const PetscReal *, PetscReal *);
128 PETSC_EXTERN PetscErrorCode PetscDTAltVWedge(PetscInt, PetscInt, PetscInt, const PetscReal *, const PetscReal *, PetscReal *);
129 PETSC_EXTERN PetscErrorCode PetscDTAltVWedgeMatrix(PetscInt, PetscInt, PetscInt, const PetscReal *, PetscReal *);
130 PETSC_EXTERN PetscErrorCode PetscDTAltVPullback(PetscInt, PetscInt, const PetscReal *, PetscInt, const PetscReal *, PetscReal *);
131 PETSC_EXTERN PetscErrorCode PetscDTAltVPullbackMatrix(PetscInt, PetscInt, const PetscReal *, PetscInt, PetscReal *);
132 PETSC_EXTERN PetscErrorCode PetscDTAltVInterior(PetscInt, PetscInt, const PetscReal *, const PetscReal *, PetscReal *);
133 PETSC_EXTERN PetscErrorCode PetscDTAltVInteriorMatrix(PetscInt, PetscInt, const PetscReal *, PetscReal *);
134 PETSC_EXTERN PetscErrorCode PetscDTAltVInteriorPattern(PetscInt, PetscInt, PetscInt (*)[3]);
135 PETSC_EXTERN PetscErrorCode PetscDTAltVStar(PetscInt, PetscInt, PetscInt, const PetscReal *, PetscReal *);
136 
137 PETSC_EXTERN PetscErrorCode PetscDTBaryToIndex(PetscInt,PetscInt,const PetscInt[],PetscInt*);
138 PETSC_EXTERN PetscErrorCode PetscDTIndexToBary(PetscInt,PetscInt,PetscInt,PetscInt[]);
139 PETSC_EXTERN PetscErrorCode PetscDTGradedOrderToIndex(PetscInt,const PetscInt[],PetscInt*);
140 PETSC_EXTERN PetscErrorCode PetscDTIndexToGradedOrder(PetscInt,PetscInt,PetscInt[]);
141 
142 #if defined(PETSC_USE_64BIT_INDICES)
143 #define PETSC_FACTORIAL_MAX 20
144 #define PETSC_BINOMIAL_MAX  61
145 #else
146 #define PETSC_FACTORIAL_MAX 12
147 #define PETSC_BINOMIAL_MAX  29
148 #endif
149 
150 /*MC
151    PetscDTFactorial - Approximate n! as a real number
152 
153    Input Parameter:
154 .  n - a non-negative integer
155 
156    Output Parameter:
157 .  factorial - n!
158 
159    Level: beginner
160 M*/
161 static inline PetscErrorCode PetscDTFactorial(PetscInt n, PetscReal *factorial)
162 {
163   PetscReal f = 1.0;
164 
165   PetscFunctionBegin;
166   *factorial = -1.0;
167   PetscCheck(n >= 0,PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Factorial called with negative number %" PetscInt_FMT, n);
168   for (PetscInt i = 1; i < n+1; ++i) f *= (PetscReal)i;
169   *factorial = f;
170   PetscFunctionReturn(0);
171 }
172 
173 /*MC
174    PetscDTFactorialInt - Compute n! as an integer
175 
176    Input Parameter:
177 .  n - a non-negative integer
178 
179    Output Parameter:
180 .  factorial - n!
181 
182    Level: beginner
183 
184    Note: 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.
185 M*/
186 static inline PetscErrorCode PetscDTFactorialInt(PetscInt n, PetscInt *factorial)
187 {
188   PetscInt facLookup[13] = {1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 3628800, 39916800, 479001600};
189 
190   PetscFunctionBegin;
191   *factorial = -1;
192   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);
193   if (n <= 12) {
194     *factorial = facLookup[n];
195   } else {
196     PetscInt f = facLookup[12];
197     PetscInt i;
198 
199     for (i = 13; i < n+1; ++i) f *= i;
200     *factorial = f;
201   }
202   PetscFunctionReturn(0);
203 }
204 
205 /*MC
206    PetscDTBinomial - Approximate the binomial coefficient "n choose k"
207 
208    Input Parameters:
209 +  n - a non-negative integer
210 -  k - an integer between 0 and n, inclusive
211 
212    Output Parameter:
213 .  binomial - approximation of the binomial coefficient n choose k
214 
215    Level: beginner
216 M*/
217 static inline PetscErrorCode PetscDTBinomial(PetscInt n, PetscInt k, PetscReal *binomial)
218 {
219   PetscFunctionBeginHot;
220   *binomial = -1.0;
221   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);
222   if (n <= 3) {
223     PetscInt binomLookup[4][4] = {{1, 0, 0, 0}, {1, 1, 0, 0}, {1, 2, 1, 0}, {1, 3, 3, 1}};
224 
225     *binomial = (PetscReal)binomLookup[n][k];
226   } else {
227     PetscReal binom = 1.0;
228 
229     k = PetscMin(k, n - k);
230     for (PetscInt i = 0; i < k; i++) binom = (binom * (PetscReal)(n - i)) / (PetscReal)(i + 1);
231     *binomial = binom;
232   }
233   PetscFunctionReturn(0);
234 }
235 
236 /*MC
237    PetscDTBinomialInt - Compute the binomial coefficient "n choose k"
238 
239    Input Parameters:
240 +  n - a non-negative integer
241 -  k - an integer between 0 and n, inclusive
242 
243    Output Parameter:
244 .  binomial - the binomial coefficient n choose k
245 
246    Note: this is limited by integers that can be represented by PetscInt
247 
248    Level: beginner
249 M*/
250 static inline PetscErrorCode PetscDTBinomialInt(PetscInt n, PetscInt k, PetscInt *binomial)
251 {
252   PetscInt bin;
253 
254   PetscFunctionBegin;
255   *binomial = -1;
256   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);
257   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);
258   if (n <= 3) {
259     PetscInt binomLookup[4][4] = {{1, 0, 0, 0}, {1, 1, 0, 0}, {1, 2, 1, 0}, {1, 3, 3, 1}};
260 
261     bin = binomLookup[n][k];
262   } else {
263     PetscInt binom = 1;
264 
265     k = PetscMin(k, n - k);
266     for (PetscInt i = 0; i < k; i++) binom = (binom * (n - i)) / (i + 1);
267     bin = binom;
268   }
269   *binomial = bin;
270   PetscFunctionReturn(0);
271 }
272 
273 /*MC
274    PetscDTEnumPerm - Get a permutation of n integers from its encoding into the integers [0, n!) as a sequence of swaps.
275 
276    A permutation can be described by the operations that convert the lists [0, 1, ..., n-1] into the permutation,
277    by a sequence of swaps, where the ith step swaps whatever number is in ith position with a number that is in
278    some position j >= i.  This swap is encoded as the difference (j - i).  The difference d_i at step i is less than
279    (n - i).  This sequence of n-1 differences [d_0, ..., d_{n-2}] is encoded as the number
280    (n-1)! * d_0 + (n-2)! * d_1 + ... + 1! * d_{n-2}.
281 
282    Input Parameters:
283 +  n - a non-negative integer (see note about limits below)
284 -  k - an integer in [0, n!)
285 
286    Output Parameters:
287 +  perm - the permuted list of the integers [0, ..., n-1]
288 -  isOdd - if not NULL, returns wether the permutation used an even or odd number of swaps.
289 
290    Note: 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.
291 
292    Level: beginner
293 M*/
294 static inline PetscErrorCode PetscDTEnumPerm(PetscInt n, PetscInt k, PetscInt *perm, PetscBool *isOdd)
295 {
296   PetscInt  odd = 0;
297   PetscInt  i;
298   PetscInt  work[PETSC_FACTORIAL_MAX];
299   PetscInt *w;
300 
301   PetscFunctionBegin;
302   if (isOdd) *isOdd = PETSC_FALSE;
303   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);
304   w = &work[n - 2];
305   for (i = 2; i <= n; i++) {
306     *(w--) = k % i;
307     k /= i;
308   }
309   for (i = 0; i < n; i++) perm[i] = i;
310   for (i = 0; i < n - 1; i++) {
311     PetscInt s = work[i];
312     PetscInt swap = perm[i];
313 
314     perm[i] = perm[i + s];
315     perm[i + s] = swap;
316     odd ^= (!!s);
317   }
318   if (isOdd) *isOdd = odd ? PETSC_TRUE : PETSC_FALSE;
319   PetscFunctionReturn(0);
320 }
321 
322 /*MC
323    PetscDTPermIndex - Encode a permutation of n into an integer in [0, n!).  This inverts PetscDTEnumPerm.
324 
325    Input Parameters:
326 +  n - a non-negative integer (see note about limits below)
327 -  perm - the permuted list of the integers [0, ..., n-1]
328 
329    Output Parameters:
330 +  k - an integer in [0, n!)
331 -  isOdd - if not NULL, returns wether the permutation used an even or odd number of swaps.
332 
333    Note: 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.
334 
335    Level: beginner
336 M*/
337 static inline PetscErrorCode PetscDTPermIndex(PetscInt n, const PetscInt *perm, PetscInt *k, PetscBool *isOdd)
338 {
339   PetscInt  odd = 0;
340   PetscInt  i, idx;
341   PetscInt  work[PETSC_FACTORIAL_MAX];
342   PetscInt  iwork[PETSC_FACTORIAL_MAX];
343 
344   PetscFunctionBeginHot;
345   *k = -1;
346   if (isOdd) *isOdd = PETSC_FALSE;
347   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);
348   for (i = 0; i < n; i++) work[i] = i;  /* partial permutation */
349   for (i = 0; i < n; i++) iwork[i] = i; /* partial permutation inverse */
350   for (idx = 0, i = 0; i < n - 1; i++) {
351     PetscInt j = perm[i];
352     PetscInt icur = work[i];
353     PetscInt jloc = iwork[j];
354     PetscInt diff = jloc - i;
355 
356     idx = idx * (n - i) + diff;
357     /* swap (i, jloc) */
358     work[i] = j;
359     work[jloc] = icur;
360     iwork[j] = i;
361     iwork[icur] = jloc;
362     odd ^= (!!diff);
363   }
364   *k = idx;
365   if (isOdd) *isOdd = odd ? PETSC_TRUE : PETSC_FALSE;
366   PetscFunctionReturn(0);
367 }
368 
369 /*MC
370    PetscDTEnumSubset - Get an ordered subset of the integers [0, ..., n - 1] from its encoding as an integers in [0, n choose k).
371    The encoding is in lexicographic order.
372 
373    Input Parameters:
374 +  n - a non-negative integer (see note about limits below)
375 .  k - an integer in [0, n]
376 -  j - an index in [0, n choose k)
377 
378    Output Parameter:
379 .  subset - the jth subset of size k of the integers [0, ..., n - 1]
380 
381    Note: this is limited by arguments such that n choose k can be represented by PetscInt
382 
383    Level: beginner
384 
385 .seealso: `PetscDTSubsetIndex()`
386 M*/
387 static inline PetscErrorCode PetscDTEnumSubset(PetscInt n, PetscInt k, PetscInt j, PetscInt *subset)
388 {
389   PetscInt Nk;
390 
391   PetscFunctionBeginHot;
392   PetscCall(PetscDTBinomialInt(n, k, &Nk));
393   for (PetscInt i = 0, l = 0; i < n && l < k; i++) {
394     PetscInt Nminuskminus = (Nk * (k - l)) / (n - i);
395     PetscInt Nminusk = Nk - Nminuskminus;
396 
397     if (j < Nminuskminus) {
398       subset[l++] = i;
399       Nk = Nminuskminus;
400     } else {
401       j -= Nminuskminus;
402       Nk = Nminusk;
403     }
404   }
405   PetscFunctionReturn(0);
406 }
407 
408 /*MC
409    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.  This is the inverse of PetscDTEnumSubset.
410 
411    Input Parameters:
412 +  n - a non-negative integer (see note about limits below)
413 .  k - an integer in [0, n]
414 -  subset - an ordered subset of the integers [0, ..., n - 1]
415 
416    Output Parameter:
417 .  index - the rank of the subset in lexicographic order
418 
419    Note: this is limited by arguments such that n choose k can be represented by PetscInt
420 
421    Level: beginner
422 
423 .seealso: `PetscDTEnumSubset()`
424 M*/
425 static inline PetscErrorCode PetscDTSubsetIndex(PetscInt n, PetscInt k, const PetscInt *subset, PetscInt *index)
426 {
427   PetscInt j = 0, Nk;
428 
429   PetscFunctionBegin;
430   *index = -1;
431   PetscCall(PetscDTBinomialInt(n, k, &Nk));
432   for (PetscInt i = 0, l = 0; i < n && l < k; i++) {
433     PetscInt Nminuskminus = (Nk * (k - l)) / (n - i);
434     PetscInt Nminusk = Nk - Nminuskminus;
435 
436     if (subset[l] == i) {
437       l++;
438       Nk = Nminuskminus;
439     } else {
440       j += Nminuskminus;
441       Nk = Nminusk;
442     }
443   }
444   *index = j;
445   PetscFunctionReturn(0);
446 }
447 
448 /*MC
449    PetscDTEnumSubset - 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.
450 
451    Input Parameters:
452 +  n - a non-negative integer (see note about limits below)
453 .  k - an integer in [0, n]
454 -  j - an index in [0, n choose k)
455 
456    Output Parameters:
457 +  perm - the jth subset of size k of the integers [0, ..., n - 1], followed by its complementary set.
458 -  isOdd - if not NULL, return whether perm is an even or odd permutation.
459 
460    Note: this is limited by arguments such that n choose k can be represented by PetscInt
461 
462    Level: beginner
463 
464 .seealso: `PetscDTEnumSubset()`, `PetscDTSubsetIndex()`
465 M*/
466 static inline PetscErrorCode PetscDTEnumSplit(PetscInt n, PetscInt k, PetscInt j, PetscInt *perm, PetscBool *isOdd)
467 {
468   PetscInt i, l, m, Nk, odd = 0;
469   PetscInt *subcomp = perm+k;
470 
471   PetscFunctionBegin;
472   if (isOdd) *isOdd = PETSC_FALSE;
473   PetscCall(PetscDTBinomialInt(n, k, &Nk));
474   for (i = 0, l = 0, m = 0; i < n && l < k; i++) {
475     PetscInt Nminuskminus = (Nk * (k - l)) / (n - i);
476     PetscInt Nminusk = Nk - Nminuskminus;
477 
478     if (j < Nminuskminus) {
479       perm[l++] = i;
480       Nk = Nminuskminus;
481     } else {
482       subcomp[m++] = i;
483       j -= Nminuskminus;
484       odd ^= ((k - l) & 1);
485       Nk = Nminusk;
486     }
487   }
488   for (; i < n; i++) subcomp[m++] = i;
489   if (isOdd) *isOdd = odd ? PETSC_TRUE : PETSC_FALSE;
490   PetscFunctionReturn(0);
491 }
492 
493 struct _p_PetscTabulation {
494   PetscInt    K;    /* Indicates a k-jet, namely tabulated derivatives up to order k */
495   PetscInt    Nr;   /* The number of tabulation replicas (often 1) */
496   PetscInt    Np;   /* The number of tabulation points in a replica */
497   PetscInt    Nb;   /* The number of functions tabulated */
498   PetscInt    Nc;   /* The number of function components */
499   PetscInt    cdim; /* The coordinate dimension */
500   PetscReal **T;    /* The tabulation T[K] of functions and their derivatives
501                        T[0] = B[Nr*Np][Nb][Nc]:             The basis function values at quadrature points
502                        T[1] = D[Nr*Np][Nb][Nc][cdim]:       The basis function derivatives at quadrature points
503                        T[2] = H[Nr*Np][Nb][Nc][cdim][cdim]: The basis function second derivatives at quadrature points */
504 };
505 typedef struct _p_PetscTabulation *PetscTabulation;
506 
507 typedef PetscErrorCode (*PetscProbFunc)(const PetscReal[], const PetscReal[], PetscReal[]);
508 
509 typedef enum {DTPROB_DENSITY_CONSTANT, DTPROB_DENSITY_GAUSSIAN, DTPROB_DENSITY_MAXWELL_BOLTZMANN, DTPROB_NUM_DENSITY} DTProbDensityType;
510 PETSC_EXTERN const char * const DTProbDensityTypes[];
511 
512 PETSC_EXTERN PetscErrorCode PetscPDFMaxwellBoltzmann1D(const PetscReal[], const PetscReal[], PetscReal[]);
513 PETSC_EXTERN PetscErrorCode PetscCDFMaxwellBoltzmann1D(const PetscReal[], const PetscReal[], PetscReal[]);
514 PETSC_EXTERN PetscErrorCode PetscPDFMaxwellBoltzmann2D(const PetscReal[], const PetscReal[], PetscReal[]);
515 PETSC_EXTERN PetscErrorCode PetscCDFMaxwellBoltzmann2D(const PetscReal[], const PetscReal[], PetscReal[]);
516 PETSC_EXTERN PetscErrorCode PetscPDFMaxwellBoltzmann3D(const PetscReal[], const PetscReal[], PetscReal[]);
517 PETSC_EXTERN PetscErrorCode PetscCDFMaxwellBoltzmann3D(const PetscReal[], const PetscReal[], PetscReal[]);
518 PETSC_EXTERN PetscErrorCode PetscPDFGaussian1D(const PetscReal[], const PetscReal[], PetscReal[]);
519 PETSC_EXTERN PetscErrorCode PetscCDFGaussian1D(const PetscReal[], const PetscReal[], PetscReal[]);
520 PETSC_EXTERN PetscErrorCode PetscPDFSampleGaussian1D(const PetscReal[], const PetscReal[], PetscReal[]);
521 PETSC_EXTERN PetscErrorCode PetscPDFGaussian2D(const PetscReal[], const PetscReal[], PetscReal[]);
522 PETSC_EXTERN PetscErrorCode PetscPDFSampleGaussian2D(const PetscReal[], const PetscReal[], PetscReal[]);
523 PETSC_EXTERN PetscErrorCode PetscPDFGaussian3D(const PetscReal[], const PetscReal[], PetscReal[]);
524 PETSC_EXTERN PetscErrorCode PetscPDFSampleGaussian3D(const PetscReal[], const PetscReal[], PetscReal[]);
525 PETSC_EXTERN PetscErrorCode PetscPDFConstant1D(const PetscReal[], const PetscReal[], PetscReal[]);
526 PETSC_EXTERN PetscErrorCode PetscCDFConstant1D(const PetscReal[], const PetscReal[], PetscReal[]);
527 PETSC_EXTERN PetscErrorCode PetscPDFSampleConstant1D(const PetscReal[], const PetscReal[], PetscReal[]);
528 PETSC_EXTERN PetscErrorCode PetscPDFConstant2D(const PetscReal[], const PetscReal[], PetscReal[]);
529 PETSC_EXTERN PetscErrorCode PetscCDFConstant2D(const PetscReal[], const PetscReal[], PetscReal[]);
530 PETSC_EXTERN PetscErrorCode PetscPDFSampleConstant2D(const PetscReal[], const PetscReal[], PetscReal[]);
531 PETSC_EXTERN PetscErrorCode PetscPDFConstant3D(const PetscReal[], const PetscReal[], PetscReal[]);
532 PETSC_EXTERN PetscErrorCode PetscCDFConstant3D(const PetscReal[], const PetscReal[], PetscReal[]);
533 PETSC_EXTERN PetscErrorCode PetscPDFSampleConstant3D(const PetscReal[], const PetscReal[], PetscReal[]);
534 PETSC_EXTERN PetscErrorCode PetscProbCreateFromOptions(PetscInt, const char[], const char[], PetscProbFunc *, PetscProbFunc *, PetscProbFunc *);
535 
536 #include <petscvec.h>
537 
538 PETSC_EXTERN PetscErrorCode PetscProbComputeKSStatistic(Vec, PetscProbFunc, PetscReal *);
539 
540 #endif
541