From 76e39c826f58120c902f1209549353cde9c3a127 Mon Sep 17 00:00:00 2001
From: Olivier Parcollet <olivier.parcollet@cea.fr>
Date: Sun, 16 Feb 2014 15:43:50 +0100
Subject: [PATCH] arrays: add make_unit_matrix and norm2, norm2_sqr

---
 triqs/arrays/matrix.hpp |  8 ++++++++
 triqs/arrays/vector.hpp | 14 ++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/triqs/arrays/matrix.hpp b/triqs/arrays/matrix.hpp
index 0b50b15b..34d1aeb6 100644
--- a/triqs/arrays/matrix.hpp
+++ b/triqs/arrays/matrix.hpp
@@ -208,6 +208,14 @@ namespace triqs { namespace arrays {
 #undef _IMPL_MATRIX_COMMON
 #undef IMPL_TYPE
 
+
+ template<typename V>
+  matrix <V> make_unit_matrix(int dim) {
+  matrix<V> r(dim, dim);
+  r() = 1;
+  return r;
+  }
+
  template<typename ArrayType>
   matrix_view<typename ArrayType::value_type, ArrayType::opt_flags, ArrayType::traversal_order>
   make_matrix_view(ArrayType const & a) { 
diff --git a/triqs/arrays/vector.hpp b/triqs/arrays/vector.hpp
index e5009355..74b530d2 100644
--- a/triqs/arrays/vector.hpp
+++ b/triqs/arrays/vector.hpp
@@ -223,6 +223,20 @@ namespace triqs { namespace arrays {
 #include "./blas_lapack/axpy.hpp"
 namespace triqs { namespace arrays {
 
+ // norm2 squared
+ template <typename V> typename std::enable_if<ImmutableVector<V>::value, typename V::value_type>::type norm2_sqr(V const& a) {
+  int dim = a.size();
+  auto r = typename V::value_type{};
+  for (int i = 0; i < dim; ++i) r += a(i) * a(i);
+  return r;
+ }
+ 
+ // norm2
+ template <typename V> typename std::enable_if<ImmutableVector<V>::value, typename V::value_type>::type norm2(V const& a) {
+  using std::sqrt;
+  return sqrt(norm2(a));
+ }
+
  // lexicographical comparison operators
  template<typename V1, typename V2>
   typename std::enable_if< ImmutableVector<V1>::value &&  ImmutableVector<V2>::value , bool>::type