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cholesky_factor_constrain.hpp
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1 #ifndef STAN_MATH_PRIM_MAT_FUN_CHOLESKY_FACTOR_CONSTRAIN_HPP
2 #define STAN_MATH_PRIM_MAT_FUN_CHOLESKY_FACTOR_CONSTRAIN_HPP
3
4 #include <stan/math/prim/mat/fun/Eigen.hpp>
5 #include <stan/math/prim/mat/fun/sum.hpp>
6 #include <cmath>
7 #include <stdexcept>
8 #include <vector>
9
10 namespace stan {
11
12 namespace math {
13
14 // CHOLESKY FACTOR
15
27 template <typename T>
28 Eigen::Matrix<T, Eigen::Dynamic, Eigen::Dynamic>
29 cholesky_factor_constrain(const Eigen::Matrix<T, Eigen::Dynamic, 1>& x,
30 int M,
31 int N) {
32 using std::exp;
33 if (M < N)
34 throw std::domain_error("cholesky_factor_constrain: "
35 "num rows must be >= num cols");
36 if (x.size() != ((N * (N + 1)) / 2 + (M - N) * N))
37 throw std::domain_error("cholesky_factor_constrain: x.size() must"
38 " be (N * (N + 1)) / 2 + (M - N) * N");
39 Eigen::Matrix<T, Eigen::Dynamic, Eigen::Dynamic> y(M, N);
40 T zero(0);
41 int pos = 0;
42 // upper square
43 for (int m = 0; m < N; ++m) {
44 for (int n = 0; n < m; ++n)
45 y(m, n) = x(pos++);
46 y(m, m) = exp(x(pos++));
47 for (int n = m + 1; n < N; ++n)
48 y(m, n) = zero;
49 }
50 // lower rectangle
51 for (int m = N; m < M; ++m)
52 for (int n = 0; n < N; ++n)
53 y(m, n) = x(pos++);
54 return y;
55 }
56
71 template <typename T>
72 Eigen::Matrix<T, Eigen::Dynamic, Eigen::Dynamic>
73 cholesky_factor_constrain(const Eigen::Matrix<T, Eigen::Dynamic, 1>& x,
74 int M,
75 int N,
76 T& lp) {
77 // cut-and-paste from above, so checks twice
78
79 using stan::math::sum;
80 if (x.size() != ((N * (N + 1)) / 2 + (M - N) * N))
81 throw std::domain_error("cholesky_factor_constrain: x.size() "
82 "must be (k choose 2) + k");
83 int pos = 0;
84 std::vector<T> log_jacobians(N);
85 for (int n = 0; n < N; ++n) {
86 pos += n;
87 log_jacobians[n] = x(pos++);
88 }
89 lp += sum(log_jacobians); // optimized for autodiff vs. direct lp +=
90 return cholesky_factor_constrain(x, M, N);
91 }
92
93
94 }
95
96 }
97
98 #endif
stan::math::sum
fvar< T > sum(const std::vector< fvar< T > > &m)
Return the sum of the entries of the specified standard vector.
Definition: sum.hpp:20
stan
Definition: log_sum_exp.hpp:8
stan::math::cholesky_factor_constrain
Eigen::Matrix< T, Eigen::Dynamic, Eigen::Dynamic > cholesky_factor_constrain(const Eigen::Matrix< T, Eigen::Dynamic, 1 > &x, int M, int N)
Return the Cholesky factor of the specified size read from the specified vector.
Definition: cholesky_factor_constrain.hpp:29
stan::math::exp
fvar< T > exp(const fvar< T > &x)
Definition: exp.hpp:10
stan::math::domain_error
void domain_error(const char *function, const char *name, const T &y, const char *msg1, const char *msg2)
Throw a domain error with a consistently formatted message.
Definition: domain_error.hpp:32
Eigen.hpp
sum.hpp

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