/* Local variables */ const Index m = s.rows(); const Index n = s.cols();
Index i, j=1;
Scalar temp;
JacobiRotation<Scalar> givens;
// r1updt had a broader usecase, but we don't use it here. And, more // importantly, we can not test it.
eigen_assert(m==n);
eigen_assert(u.size()==m);
eigen_assert(v.size()==n);
eigen_assert(w.size()==n);
/* move the nontrivial part of the last column of s into w. */
w[n-1] = s(n-1,n-1);
/* rotate the vector v into a multiple of the n-th unit vector */ /* in such a way that a spike is introduced into w. */ for (j=n-2; j>=0; --j) {
w[j] = 0.; if (v[j] != 0.) { /* determine a givens rotation which eliminates the */ /* j-th element of v. */
givens.makeGivens(-v[n-1], v[j]);
/* apply the transformation to v and store the information */ /* necessary to recover the givens rotation. */
v[n-1] = givens.s() * v[j] + givens.c() * v[n-1];
v_givens[j] = givens;
/* apply the transformation to s and extend the spike in w. */ for (i = j; i < m; ++i) {
temp = givens.c() * s(j,i) - givens.s() * w[i];
w[i] = givens.s() * s(j,i) + givens.c() * w[i];
s(j,i) = temp;
}
} else
v_givens[j] = IdentityRotation;
}
/* add the spike from the rank 1 update to w. */
w += v[n-1] * u;
/* eliminate the spike. */
*sing = false; for (j = 0; j < n-1; ++j) { if (w[j] != 0.) { /* determine a givens rotation which eliminates the */ /* j-th element of the spike. */
givens.makeGivens(-s(j,j), w[j]);
/* apply the transformation to s and reduce the spike in w. */ for (i = j; i < m; ++i) {
temp = givens.c() * s(j,i) + givens.s() * w[i];
w[i] = -givens.s() * s(j,i) + givens.c() * w[i];
s(j,i) = temp;
}
/* store the information necessary to recover the */ /* givens rotation. */
w_givens[j] = givens;
} else
v_givens[j] = IdentityRotation;
/* test for zero diagonal elements in the output s. */ if (s(j,j) == 0.) {
*sing = true;
}
} /* move w back into the last column of the output s. */
s(n-1,n-1) = w[n-1];
if (s(j,j) == 0.) {
*sing = true;
} return;
}
} // end namespace internal
} // end namespace Eigen
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