Fixed AVX2 support for radec2lmn.

We have to make sure that SmartVector is actually aligned. Then we
can switch back to the aligned mode. The current implementation does not
guarantee that the data is aligned.

include/Directions.h

@@ -14,6 +14,7 @@
 #include <common/SmartVector.h>
 
 #include <vector>
+#include <xsimd/types/xsimd_avx512f_register.hpp>
 #include <xtensor/xmath.hpp>
 #include <xtensor/xview.hpp>
 
@@ -145,16 +146,18 @@ struct radec2lmn {
 template <class C, class Tag, class Arch>
 void radec2lmn::operator()(Arch, const Direction &reference, const C &ra,
                            const C &dec, xt::xtensor<double, 2> &lmn, Tag) {
-  using b_type = xsimd::batch<double, Arch>;
+  using b_type = xsimd::batch<double>;
   std::size_t inc = b_type::size;
   std::size_t size = ra.size();
-  double sin_dec0 = std::sin(reference.dec);
-  double cos_dec0 = std::cos(reference.dec);
+  const double sin_dec0 = std::sin(reference.dec);
+  const double cos_dec0 = std::cos(reference.dec);
+
+  const ConstSmartVectorView<double> ra_view = ra.view();
   // size for which the vectorization is possible
   std::size_t vec_size = size - size % inc;
   for (std::size_t i = 0; i < vec_size; i += inc) {
-    const b_type ra_vec = b_type::load(&ra[i], Tag());
-    const b_type dec_vec = b_type::load(&dec[i], Tag());
+    const b_type ra_vec = b_type::load(&(ra_view[i]), Tag());
+    const b_type dec_vec = b_type::load(&(dec[i]), Tag());
 
     const b_type delta_ra = ra_vec - reference.ra;
 
@@ -196,8 +199,22 @@ template <>
 inline void Directions::radec2lmn<Directions::computation_strategy::MULTI_SIMD>(
     const Direction &reference, xt::xtensor<double, 2> &lmn) {
   xt::xtensor<double, 2> lmn_tmp({3, ra.size()});
-  xsimd::dispatch(xsimd::radec2lmn{})(reference, ra, dec, lmn_tmp,
-                                      xsimd::aligned_mode());
+
+  // FIXME: we have to make sure that SmartVector is actually aligned. Then we
+  // can switch back to the aligned mode. The current implementation does not
+  // guarantee that the data is aligned.
+  if (reinterpret_cast<std::uintptr_t>(ra.data()) %
+          xsimd::arch_list<xsimd::avx2>::alignment() !=
+      0) {
+    std::cerr << "Warning: ra is not aligned. Using unaligned mode."
+              << std::endl;
+    xsimd::dispatch<xsimd::arch_list<xsimd::avx2>>(xsimd::radec2lmn{})(
+        reference, ra, dec, lmn_tmp, xsimd::unaligned_mode{});
+  } else {
+    xsimd::dispatch<xsimd::arch_list<xsimd::avx2>>(xsimd::radec2lmn{})(
+        reference, ra, dec, lmn_tmp, xsimd::aligned_mode{});
+  }
+
   lmn = xt::transpose(lmn_tmp);
 }
 #endif
\ No newline at end of file

include/common/SmartVector.h

@@ -18,6 +18,10 @@ using SmartVectorView =
     decltype(::xt::adapt(std::add_pointer_t<T>{}, std::array<size_t, 1UL>{}));
 ;
 
+template <typename T>
+using ConstSmartVectorView =
+    decltype(::xt::adapt(std::declval<const T *>(), std::array<size_t, 1>{}));
+
 template <typename T> class SmartVector : public std::vector<T> {
 public:
   SmartVector() : std::vector<T>() {}
@@ -25,7 +29,7 @@ public:
   SmartVector(const std::initializer_list<T> &vec) : std::vector<T>(vec) {}
   SmartVectorView<T> view() { return xt::adapt(this->data(), {this->size()}); }
 
-  const SmartVectorView<T> view() const {
+  ConstSmartVectorView<T> view() const {
     return xt::adapt(this->data(), {this->size()});
   }