diff --git a/opm-common-prereqs.cmake b/opm-common-prereqs.cmake
index 1939eda81..82f7a7b7d 100644
--- a/opm-common-prereqs.cmake
+++ b/opm-common-prereqs.cmake
@@ -3,7 +3,8 @@
 
 # defines that must be present in config.h for our headers
 set (opm-common_CONFIG_VAR
-	"HAS_ATTRIBUTE_UNUSED")
+	HAVE_OPENMP
+	)
 
 # dependencies
 set (opm-common_DEPS
diff --git a/opm/parser/eclipse/EclipseState/Grid/EclipseGrid.hpp b/opm/parser/eclipse/EclipseState/Grid/EclipseGrid.hpp
index 93a476809..d6f3317ab 100644
--- a/opm/parser/eclipse/EclipseState/Grid/EclipseGrid.hpp
+++ b/opm/parser/eclipse/EclipseState/Grid/EclipseGrid.hpp
@@ -154,6 +154,7 @@ namespace Opm {
         std::array<double, 3> getCellCenter(size_t i,size_t j, size_t k) const;
         std::array<double, 3> getCellCenter(size_t globalIndex) const;
         std::array<double, 3> getCornerPos(size_t i,size_t j, size_t k, size_t corner_index) const;
+        std::vector<double> activeVolume() const;
         double getCellVolume(size_t globalIndex) const;
         double getCellVolume(size_t i , size_t j , size_t k) const;
         double getCellThickness(size_t globalIndex) const;
diff --git a/python/setup.py b/python/setup.py
index d88acc284..c44a8d191 100644
--- a/python/setup.py
+++ b/python/setup.py
@@ -66,7 +66,8 @@ ext_modules = [
         language='c++',
         undef_macros=["NDEBUG"],
         include_dirs=["pybind11/include"],
-        extra_compile_args=['-std=c++17']
+        extra_compile_args=['-std=c++17', '-fopenmp'],
+        extra_link_args=['-fopenmp']
     )
 ]
 
diff --git a/src/opm/parser/eclipse/EclipseState/Grid/EclipseGrid.cpp b/src/opm/parser/eclipse/EclipseState/Grid/EclipseGrid.cpp
index 6b813523e..16607ca47 100644
--- a/src/opm/parser/eclipse/EclipseState/Grid/EclipseGrid.cpp
+++ b/src/opm/parser/eclipse/EclipseState/Grid/EclipseGrid.cpp
@@ -1343,8 +1343,23 @@ std::vector<double> EclipseGrid::createDVector(const std::array<int,3>& dims, st
         assertIJK(i,j,k);
 
         size_t globalIndex = getGlobalIndex(i,j,k);
+        return this->cellActive(globalIndex);
+    }
 
-        return m_actnum[globalIndex]>0;
+    std::vector<double> EclipseGrid::activeVolume() const {
+        std::vector<double> active_volume( this->m_nactive );
+
+        #pragma omp parallel for schedule(static)
+        for (std::size_t active_index = 0; active_index < this->m_active_to_global.size(); active_index++) {
+            std::array<double,8> X;
+            std::array<double,8> Y;
+            std::array<double,8> Z;
+            auto global_index = this->m_active_to_global[active_index];
+            this->getCellCorners(global_index, X, Y, Z );
+            active_volume[active_index] = calculateCellVol(X, Y, Z);
+        }
+
+        return active_volume;
     }
 
 
@@ -1666,9 +1681,6 @@ std::vector<double> EclipseGrid::createDVector(const std::array<int,3>& dims, st
             this->resetACTNUM();
         else {
             auto global_size = this->getCartesianSize();
-            if (this->m_actnum.empty() || std::memcmp(actnum, this->m_actnum.data(), global_size * sizeof * actnum) != 0) {
-            }
-
             this->m_global_to_active.clear();
             this->m_active_to_global.clear();
             this->m_actnum.resize(global_size);
@@ -1682,15 +1694,16 @@ std::vector<double> EclipseGrid::createDVector(const std::array<int,3>& dims, st
                     this->m_nactive++;
                 } else {
                     this->m_global_to_active.push_back(-1);
+
                 }
             }
         }
     }
 
     void EclipseGrid::resetACTNUM(const std::vector<int>& actnum) {
-        if (actnum.size() != getCartesianSize()) {
+        if (actnum.size() != getCartesianSize())
             throw std::runtime_error("resetACTNUM(): actnum vector size differs from logical cartesian size of grid.");
-        }
+
         this->resetACTNUM(actnum.data());
     }
 
diff --git a/src/opm/parser/eclipse/EclipseState/Grid/FieldProps.cpp b/src/opm/parser/eclipse/EclipseState/Grid/FieldProps.cpp
index 459018533..e8fd4afd7 100644
--- a/src/opm/parser/eclipse/EclipseState/Grid/FieldProps.cpp
+++ b/src/opm/parser/eclipse/EclipseState/Grid/FieldProps.cpp
@@ -388,10 +388,7 @@ void handle_box_keyword(const DeckKeyword& deckKeyword,  Box& box) {
 
 
 std::vector<double> extract_cell_volume(const EclipseGrid& grid) {
-    std::vector<double> cell_volume(grid.getNumActive());
-    for (std::size_t active_index = 0; active_index < grid.getNumActive(); active_index++)
-        cell_volume[active_index] = grid.getCellVolume( grid.getGlobalIndex(active_index));
-    return cell_volume;
+    return grid.activeVolume();
 }
 
 std::vector<double> extract_cell_depth(const EclipseGrid& grid) {