struct nlop_s* nlop_chain(const struct nlop_s* a, const struct nlop_s* b)
{
assert(1 == nlop_get_nr_in_args(a));
assert(1 == nlop_get_nr_out_args(a));
assert(1 == nlop_get_nr_in_args(b));
assert(1 == nlop_get_nr_out_args(b));
const struct linop_s* la = linop_from_nlop(a);
const struct linop_s* lb = linop_from_nlop(b);
if ((NULL != la) && (NULL != lb))
return nlop_from_linop(linop_chain(la, lb));
PTR_ALLOC(struct nlop_s, n);
const struct linop_s* (*der)[1][1] = TYPE_ALLOC(const struct linop_s*[1][1]);
n->derivative = &(*der)[0][0];
if (NULL == la)
la = a->derivative[0];
if (NULL == lb)
lb = b->derivative[0];
n->op = operator_chain(a->op, b->op);
n->derivative[0] = linop_chain(la, lb);
return PTR_PASS(n);
}
/**
* Create chain of linear operators.
* C = B A
* C^H = A^H B^H
* C^H C = A^H B^H B A
*/
struct linop_s* linop_chain(const struct linop_s* a, const struct linop_s* b)
{
struct linop_s* c = xmalloc(sizeof(struct linop_s));
c->forward = operator_chain(a->forward, b->forward);
c->adjoint = operator_chain(b->adjoint, a->adjoint);
if (NULL == b->normal) {
c->normal = operator_chain(c->forward, c->adjoint);
} else {
const struct operator_s* top = operator_chain(b->normal, a->adjoint);
c->normal = operator_chain(a->forward, top);
operator_free(top);
}
c->norm_inv = NULL;
return c;
}
