From dcb926d2f6ea13ddb1cac826f51fdedc70ed3698 Mon Sep 17 00:00:00 2001
From: Conrad Sanderson <conradsnicta@users.noreply.github.com>
Date: Mon, 6 Apr 2020 10:53:12 +0200
Subject: [PATCH 1/2] corrections to handle vector types in Armadillo 9.870

This patch corrects handling of Armadillo vector types by `IsVector`.
Without this patch, mlpack will not compile with Armadillo 9.870 (and development version 9.869).

Armadillo 9.870 has extended handling of sparse submatrix views. In addition to `arma::SpSubview`, it now has `arma::SpSubview_col` and `arma::SpSubview_row`.  The latter two types are vector types, so `IsVector` needs to be adjusted accordingly.
---
 src/mlpack/core/util/arma_traits.hpp | 35 +++++++++++++++++++++-------
 1 file changed, 27 insertions(+), 8 deletions(-)

diff --git a/src/mlpack/core/util/arma_traits.hpp b/src/mlpack/core/util/arma_traits.hpp
index 45e5dac125..efa59c4fd2 100644
--- a/src/mlpack/core/util/arma_traits.hpp
+++ b/src/mlpack/core/util/arma_traits.hpp
@@ -81,14 +81,33 @@ struct IsVector<arma::subview_row<eT> >
   const static bool value = true;
 };
 
-// I'm not so sure about this one.  An SpSubview object can be a row or column,
-// but it can also be a matrix subview.
 
-// template<>
-template<typename eT>
-struct IsVector<arma::SpSubview<eT> >
-{
-  const static bool value = true;
-};
+#if ( (ARMA_VERSION_MAJOR >= 10) || ((ARMA_VERSION_MAJOR == 9) && (ARMA_VERSION_MINOR >= 869)) )
+
+  // Armadillo 9.869+ has SpSubview_col and SpSubview_row
+
+  template<typename eT>
+  struct IsVector<arma::SpSubview_col<eT> >
+  {
+    const static bool value = true;
+  };
+
+  template<typename eT>
+  struct IsVector<arma::SpSubview_row<eT> >
+  {
+    const static bool value = true;
+  };
+
+#else
+
+  // fallback for older Armadillo versions
+
+  template<typename eT>
+  struct IsVector<arma::SpSubview<eT> >
+  {
+    const static bool value = true;
+  };
+
+#endif
 
 #endif

From 77a0513d1df916c9e0f9bbcd91a998a039fcdaa5 Mon Sep 17 00:00:00 2001
From: Conrad Sanderson <conradsnicta@users.noreply.github.com>
Date: Tue, 7 Apr 2020 02:56:12 +0200
Subject: [PATCH 2/2] layout changes

Co-Authored-By: Ryan Curtin <ryan@ratml.org>
---
 src/mlpack/core/util/arma_traits.hpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/mlpack/core/util/arma_traits.hpp b/src/mlpack/core/util/arma_traits.hpp
index efa59c4fd2..155a6a0d82 100644
--- a/src/mlpack/core/util/arma_traits.hpp
+++ b/src/mlpack/core/util/arma_traits.hpp
@@ -82,7 +82,8 @@ struct IsVector<arma::subview_row<eT> >
 };
 
 
-#if ( (ARMA_VERSION_MAJOR >= 10) || ((ARMA_VERSION_MAJOR == 9) && (ARMA_VERSION_MINOR >= 869)) )
+#if ((ARMA_VERSION_MAJOR >= 10) || \
+    ((ARMA_VERSION_MAJOR == 9) && (ARMA_VERSION_MINOR >= 869)))
 
   // Armadillo 9.869+ has SpSubview_col and SpSubview_row