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Atomic Reverse Hessian Sparsity Patterns

Syntax
ok = afun.rev_sparse_hes(vx, s, t, q, r, u, v, x)

Deprecated 2016-06-27
ok = afun.rev_sparse_hes(vx, s, t, q, r, u, v)

Purpose
This function is used by RevSparseHes to compute Hessian sparsity patterns. If you are using RevSparseHes to compute one of the versions of this virtual function muse be defined by the atomic_user class.  There is an unspecified scalar valued function $g : B^m \rightarrow B$. Given a sparsity pattern for $R \in B^{n \times q}$, and information about the function $z = g(y)$, this routine computes the sparsity pattern for $$V(x) = (g \circ f)^{(2)}( x ) R$$

Implementation
If you are using and RevSparseHes , this virtual function must be defined by the atomic_user class.

vx
The argument vx has prototype       const CppAD:vector<bool>& vx  vx.size() == n , and for $j = 0 , \ldots , n-1$, vx[j] is true if and only if ax[j] is a variable in the corresponding call to       afun(ax, ay) 
s
The argument s has prototype       const CppAD:vector<bool>& s  and its size is m . It is a sparsity pattern for $S(x) = g^{(1)} [ f(x) ] \in B^{1 \times m}$.

t
This argument has prototype       CppAD:vector<bool>& t  and its size is m . The input values of its elements are not specified (must not matter). Upon return, t is a sparsity pattern for $T(x) \in B^{1 \times n}$ where $$T(x) = (g \circ f)^{(1)} (x) = S(x) * f^{(1)} (x)$$

q
The argument q has prototype       size_t q  It specifies the number of columns in $R \in B^{n \times q}$, $U(x) \in B^{m \times q}$, and $V(x) \in B^{n \times q}$.

r
This argument has prototype       const atomic_sparsity& r  and is a atomic_sparsity pattern for $R \in B^{n \times q}$.

u
This argument has prototype       const atomic_sparsity& u  and is a atomic_sparsity pattern for $U(x) \in B^{m \times q}$ which is defined by $$\begin{array}{rcl} U(x) & = & \{ \partial_u \{ \partial_y g[ y + f^{(1)} (x) R u ] \}_{y=f(x)} \}_{u=0} \\ & = & \partial_u \{ g^{(1)} [ f(x) + f^{(1)} (x) R u ] \}_{u=0} \\ & = & g^{(2)} [ f(x) ] f^{(1)} (x) R \end{array}$$

v
This argument has prototype       atomic_sparsity& v  The input value of its elements are not specified (must not matter). Upon return, v is a atomic_sparsity pattern for $V(x) \in B^{n \times q}$ which is defined by $$\begin{array}{rcl} V(x) & = & \partial_u [ \partial_x (g \circ f) ( x + R u ) ]_{u=0} \\ & = & \partial_u [ (g \circ f)^{(1)}( x + R u ) ]_{u=0} \\ & = & (g \circ f)^{(2)}( x ) R \\ & = & f^{(1)} (x)^\R{T} g^{(2)} [ f(x) ] f^{(1)} (x) R + \sum_{i=1}^m g_i^{(1)} [ f(x) ] \; f_i^{(2)} (x) R \\ & = & f^{(1)} (x)^\R{T} U(x) + \sum_{i=1}^m S_i (x) \; f_i^{(2)} (x) R \end{array}$$

x
The argument has prototype       const CppAD::vector<Base>& x  and size is equal to the n . This is the Value value corresponding to the parameters in the vector ax (when the atomic function was called). To be specific, if       if( Parameter(ax[i]) == true )           x[i] = Value( ax[i] );      else           x[i] = CppAD::numeric_limits<Base>::quiet_NaN();  The version of this function with out the x argument is deprecated; i.e., you should include the argument even if you do not use it.

Examples
The file atomic_rev_sparse_hes.cpp contains an example and test that uses this routine. It returns true if the test passes and false if it fails.