From c3dabfc853269ffc52f4951debee65f2d4657472 Mon Sep 17 00:00:00 2001
From: "J.A. de Jong - Redu-Sone B.V., ASCEE V.O.F" <j.a.dejong@ascee.nl>
Date: Tue, 11 Oct 2022 09:50:15 +0200
Subject: [PATCH] Added manual Armadillo - Numpy converters

---
 src/lasp/pybind11/arma_npy.h | 132 +++++++++++++++++++++++++++++++++++
 1 file changed, 132 insertions(+)
 create mode 100644 src/lasp/pybind11/arma_npy.h

diff --git a/src/lasp/pybind11/arma_npy.h b/src/lasp/pybind11/arma_npy.h
new file mode 100644
index 0000000..4fe8920
--- /dev/null
+++ b/src/lasp/pybind11/arma_npy.h
@@ -0,0 +1,132 @@
+#pragma once
+#include "lasp_mathtypes.h"
+#include <cstring>
+#include <pybind11/numpy.h>
+#include <type_traits>
+
+namespace py = pybind11;
+
+template<typename T>
+using pyarray = py::array_t<T, py::array::f_style | py::array::forcecast>;
+using dpyarray = pyarray<d>;
+
+
+/**
+ * @brief Convert Armadillo column vector to Numpy 1D array
+ *
+ * @tparam T Type (double, d, c, etc)
+ * @param data Input Armadillo array
+ *
+ * @return Numpy array with copied data
+ */
+template <typename T> py::array_t<T> ColToNpy(const arma::Col<T> &data) {
+
+  const us Tsize = sizeof(T);
+
+  const auto nrows = static_cast<ssize_t>(data.n_rows);
+
+  const us size = nrows;
+
+  py::array_t<T> result({nrows}, {Tsize});
+
+  // Copy over memory
+  if (size > 0) {
+    memcpy(result.mutable_data(0), data.memptr(), sizeof(T) * nrows);
+  }
+
+  return result;
+}
+
+/**
+ * @brief Convert Armadillo 2D array Numpy 2D array
+ *
+ * @tparam T Type (double, d, c, etc)
+ * @param data Input Armadillo array
+ *
+ * @return Numpy array with copied data
+ */
+template <typename T> py::array_t<T> MatToNpy(const arma::Mat<T> &data) {
+
+  const us Tsize = sizeof(T);
+
+  const auto nrows = static_cast<ssize_t>(data.n_rows);
+  const auto ncols = static_cast<ssize_t>(data.n_cols);
+
+  const us size = nrows;
+
+  py::array_t<T> result({nrows, ncols}, {Tsize, nrows * Tsize});
+
+  // Copy over memory
+  if (size > 0) {
+    memcpy(result.mutable_data(0, 0), data.memptr(), sizeof(T) * nrows * ncols);
+  }
+
+  return result;
+}
+
+/**
+ * @brief Convert Armadillo Cube to Numpy 3D array
+ *
+ * @tparam T Type (double, d, c, etc)
+ * @param data Input Armadillo Array
+ *
+ * @return Numpy array with copied data
+ */
+template <typename T> py::array_t<T> CubeToNpy(const arma::Cube<T> &data) {
+
+  const us Tsize = sizeof(T);
+
+  const auto nrows = static_cast<ssize_t>(data.n_rows);
+  const auto ncols = static_cast<ssize_t>(data.n_cols);
+  const auto nslices = static_cast<ssize_t>(data.n_slices);
+
+  const us size = nrows * ncols * nslices;
+
+  py::array_t<T> result({nrows, ncols, nslices},
+                        {Tsize, nrows * Tsize, nrows * ncols * Tsize});
+
+  // Copy over memory
+  if (size > 0) {
+    memcpy(result.mutable_data(0, 0, 0), data.memptr(),
+           sizeof(T) * nrows * ncols * nslices);
+  }
+
+  return result;
+}
+
+/// BACK converters
+
+/**
+ * @brief Wrap Numpy array to 2D Armadillo Mat
+ *
+ * @tparam T Type
+ * @tparam copy Whether to copy the data. If true, creates a copy
+ * @param data The Numpy array to convert
+ *
+ * @return Mat instance
+ */
+template <typename T, bool copy = true>
+arma::Mat<T> NpyToMat(pyarray<T> data) {
+  if (data.ndim() != 2) {
+    throw std::runtime_error("Expects a 2D array");
+  }
+  return arma::Mat<T>(data.mutable_data(0,0), data.shape(0), data.shape(1), copy);
+}
+
+/**
+ * @brief Wrap Numpy array to 1D Armadillo column vector
+ *
+ * @tparam T Type
+ * @tparam copy Whether to copy the data. If true, creates a copy
+ * @param data The Numpy array to convert
+ *
+ * @return Armadillo column instance
+ */
+template <typename T, bool copy = true>
+arma::Mat<T> NpyToCol(pyarray<T> data) {
+  if (data.ndim() != 1) {
+    throw std::runtime_error("Expects a 1D array");
+  }
+  return arma::Col<d>(data.mutable_data(0), data.size(), copy);
+}
+