From ba36559d8923700fa38ebf23107f8867971870cd Mon Sep 17 00:00:00 2001
From: Daniel Sharp <dannys4@mit.edu>
Date: Fri, 16 Feb 2024 13:08:51 -0500
Subject: [PATCH] Use host view to construct multi-index

---
 MParT/MultiIndices/MultiIndex.h         | 10 ++++----
 src/MultiIndices/FixedMultiIndexSet.cpp |  7 +++---
 src/MultiIndices/MultiIndex.cpp         | 31 ++++++++++++++-----------
 3 files changed, 25 insertions(+), 23 deletions(-)

diff --git a/MParT/MultiIndices/MultiIndex.h b/MParT/MultiIndices/MultiIndex.h
index 2633033c..c8d3b336 100644
--- a/MParT/MultiIndices/MultiIndex.h
+++ b/MParT/MultiIndices/MultiIndex.h
@@ -6,6 +6,8 @@
 #include <vector>
 
 #include <Eigen/Core>
+#include <Kokkos_Core.hpp>
+#include <iostream>
 
 namespace mpart {
 
@@ -55,14 +57,12 @@ class MultiIndex {
      * 
      * @param nzIndsIn indices of the nonzero values
      * @param nzValsIn values that are nonzero
-     * @param numNz number of nonzero values (i.e., length of nzIndsIn and nzValsIn)
      * @param lengthIn dimension of the index (numNz==lengthIn iff all values are nonzero)
      */
-    MultiIndex(unsigned int* nzIndsIn,
-        unsigned int* nzValsIn,
-        unsigned int numNz,
+    MultiIndex(Kokkos::View<unsigned int*, Kokkos::HostSpace> const& nzIndsIn,
+        Kokkos::View<unsigned int*, Kokkos::HostSpace> const& nzValsIn,
         unsigned int lengthIn);
-    
+
     /** Uses a dense vector description of the multiindex, defined through a pointer,
         and extracts the nonzero components.
         @param[in] fullVec A pointer the memory containing the dense multiindex.
diff --git a/src/MultiIndices/FixedMultiIndexSet.cpp b/src/MultiIndices/FixedMultiIndexSet.cpp
index 4fe48868..a96cb3c1 100644
--- a/src/MultiIndices/FixedMultiIndexSet.cpp
+++ b/src/MultiIndices/FixedMultiIndexSet.cpp
@@ -347,10 +347,9 @@ MultiIndexSet FixedMultiIndexSet<MemorySpace>::Unfix() const
     for(int term = 0; term < h_nzStarts.extent(0)-1; term++){
         unsigned int start = h_nzStarts(term);
         unsigned int end = h_nzStarts(term+1);
-        unsigned int numNz = end - start;
-        unsigned int* nzIndTerm = h_nzDims.data() + start;
-        unsigned int* nzValTerm = h_nzOrders.data() + start;
-        MultiIndex midx_term {nzIndTerm, nzValTerm, numNz, this->dim};
+        auto nzIndTerm = Kokkos::subview(h_nzDims, Kokkos::pair<unsigned int, unsigned int>(start, end));
+        auto nzValTerm = Kokkos::subview(h_nzOrders, Kokkos::pair<unsigned int, unsigned int>(start, end));
+        MultiIndex midx_term {nzIndTerm, nzValTerm, this->dim};
         output.AddActive(midx_term);
     }
     return output;
diff --git a/src/MultiIndices/MultiIndex.cpp b/src/MultiIndices/MultiIndex.cpp
index 867fd4cd..f0fa3f97 100644
--- a/src/MultiIndices/MultiIndex.cpp
+++ b/src/MultiIndices/MultiIndex.cpp
@@ -55,21 +55,24 @@ MultiIndex::MultiIndex(std::initializer_list<unsigned int> const& indIn) : Multi
   }
 }
 
-MultiIndex::MultiIndex(unsigned int* nzIndsIn,
-                       unsigned int* nzValsIn,
-                       unsigned int numNz,
-                       unsigned int lengthIn) : length(lengthIn),
-                                                maxValue(0),
-                                                totalOrder(0)
-{
-  for(unsigned int i=0; i<numNz; ++i){
-    if(nzValsIn[i]>0){
-      nzInds.push_back(nzIndsIn[i]);
-      nzVals.push_back(nzValsIn[i]);
-      maxValue = std::max<unsigned int>(maxValue, nzValsIn[i]);
-      totalOrder += nzValsIn[i];
+MultiIndex::MultiIndex(Kokkos::View<unsigned int*, Kokkos::HostSpace> const& nzIndsIn,
+        Kokkos::View<unsigned int*, Kokkos::HostSpace> const& nzValsIn,
+        unsigned int lengthIn): length(lengthIn), maxValue(0), totalOrder(0) {
+    unsigned int numNz = nzIndsIn.size();
+    if(numNz != nzValsIn.size()){
+        std::stringstream ss;
+        ss << "MultiIndex::MultiIndex: nzIndsIn and nzValsIn must have the same number"
+            << "of elements.  Found " << numNz << " and " << nzValsIn.size() << " elements.";
+        throw std::runtime_error(ss.str().c_str());
+    }
+    for(unsigned int i=0; i<numNz; ++i){
+        if(nzValsIn(i)>0){
+            nzInds.push_back(nzIndsIn(i));
+            nzVals.push_back(nzValsIn(i));
+            maxValue = std::max<unsigned int>(maxValue, nzValsIn(i));
+            totalOrder += nzValsIn(i);
+        }
     }
-  }
 }
 
 std::vector<unsigned int>MultiIndex::Vector() const