addressing comments regarding the FastSmallVector::expandSize

it is renamed to a more general resize and the function is revised
accordingly.

Author: GitPaean

opm/material/common/FastSmallVector.hpp

@@ -99,7 +99,7 @@ class FastSmallVector
     FastSmallVector& operator=(FastSmallVector&& other)
     {
         size_ = other.size_;
-        if (size_ <= N) {
+        if (other.usingSmallBuf()) {
             smallBuf_ = std::move(other.smallBuf_);
             dataPtr_ = smallBuf_.data();
         }
@@ -119,7 +119,7 @@ class FastSmallVector
     {
         size_ = other.size_;
 
-        if (size_ <= N) {
+        if (other.usingSmallBuf()) {
             smallBuf_ = other.smallBuf_;
             dataPtr_ = smallBuf_.data();
         }
@@ -176,20 +176,22 @@ class FastSmallVector
     { return dataPtr_ + size_; }
 
     size_type capacity()
-    { return size_ <= N ? N : data_.capacity(); }
+    { return this->usingSmallBuf() ? N : data_.capacity(); }
 
     void push_back(const ValueType& value)
     {
-        if (size_ < N) {
-            // Data is contained in smallBuf_
-            smallBuf_[size_++] = value;
-        } else if (size_ == N) {
-            // Must switch from using smallBuf_ to using data_
-            data_.reserve(N + 1);
-            data_.assign(smallBuf_.begin(), smallBuf_.end());
-            data_.push_back(value);
-            ++size_;
-            dataPtr_ = data_.data();
+        if (this->usingSmallBuf()) {
+            if (size_ < N) {
+                // Data is contained in smallBuf_
+                smallBuf_[size_++] = value;
+            } else if (size_ == N) {
+                // Must switch from using smallBuf_ to using data_
+                data_.reserve(N + 1);
+                data_.assign(smallBuf_.begin(), smallBuf_.end());
+                data_.push_back(value);
+                ++size_;
+                dataPtr_ = data_.data();
+            }
         } else {
             // Data is contained in data_
             data_.push_back(value);
@@ -198,17 +200,23 @@ class FastSmallVector
         }
     }
 
-    void expandSize(size_t numElem)
+    void resize(size_t numElem)
     {
-        assert(numElem >= size_);
-        if (size_ <= N) {
+        if (numElem == size_) return; // nothing to do
+
+        if (this->usingSmallBuf()) {
             if (numElem > N) {
-                data_.resize(numElem, 0);
-                data_.assign(smallBuf_.begin(), smallBuf_.begin() + size_);
+                data_.resize(numElem);
+                std::copy(smallBuf_.begin(), smallBuf_.begin() + size_, data_.begin());
                 dataPtr_ = data_.data();
+            } else if (numElem < size_) {
+                // when shrinking, remove the values after numElem so that the space
+                // is ready to use in the potentional future resize
+                std::fill(smallBuf_.begin() + numElem, smallBuf_.begin() + size_, ValueType{});
             }
         } else {
-            data_.resize(numElem, 0);
+            // when shriking to numElem < N, we do not switch back to use smallBuf_
+            data_.resize(numElem);
         }
         size_ = numElem;
     }
@@ -225,6 +233,11 @@ class FastSmallVector
             dataPtr_ = smallBuf_.data();
     }
 
+    bool usingSmallBuf() const
+    {
+        return dataPtr_ == smallBuf_.data();
+    }
+
     std::array<ValueType, N> smallBuf_{};
     std::vector<ValueType> data_;
     size_type size_;

opm/material/densead/DynamicEvaluation.hpp

@@ -691,7 +691,7 @@ class Evaluation<ValueT, DynamicSize, staticSize>
     void appendDerivativesToConstant(size_t numDer) {
         assert(size() == 0); // we only append derivatives to a constant
         if (numDer > 0) {
-            data_.expandSize(1 + numDer);
+            data_.resize(1 + numDer);
         }
     }
 };