1 files changed, 15 insertions, 0 deletions
diff --git a/p-spin.hpp b/p-spin.hpp
index b2bdf07..e5cd195 100644
--- a/p-spin.hpp
+++ b/p-spin.hpp
@@ -89,3 +89,18 @@ std::tuple<Real, Vector<Scalar>> WdW(const Tensor<Scalar, p>& J, const Vector<Sc
 
   return {W, dW};
 }
+
+template <class Scalar>
+Matrix<Scalar> dzDot(const Vector<Scalar>& z, const Vector<Scalar>& dH) {
+  Real z² = z.squaredNorm();
+  return (dH.conjugate() - (dH.dot(z) / z²) * z.conjugate()) * z.adjoint() / z²;
+}
+
+template <class Scalar>
+Matrix<Scalar> dzDotConjugate(const Vector<Scalar>& z, const Vector<Scalar>& dH, const Matrix<Scalar>& ddH) {
+  Real z² = z.squaredNorm();
+  return -ddH + (ddH * z.conjugate()) * z.transpose() / z²
+          + (z.dot(dH) / z²) * (
+              Matrix<Scalar>::Identity(ddH.rows(), ddH.cols()) - z.conjugate() * z.transpose() / z²
+            );
+}