From 6c47b22cc3e6731792364fba8f913e3ef898e44c Mon Sep 17 00:00:00 2001
From: Tom Lin <tom91136@gmail.com>
Date: Fri, 12 Nov 2021 12:38:54 +0000
Subject: [PATCH] Capture vectors by reference directly Add custom range
 implementation

---
 STDStream.cpp | 45 +++++++++++++++++++++++----------------------
 STDStream.h   | 39 +++++++++++++++++++++++++++++++++++----
 2 files changed, 58 insertions(+), 26 deletions(-)

diff --git a/STDStream.cpp b/STDStream.cpp
index 30ad420..536fd1c 100644
--- a/STDStream.cpp
+++ b/STDStream.cpp
@@ -14,62 +14,61 @@
 // auto exe_policy = std::execution::par;
 auto exe_policy = std::execution::par_unseq;
 
-template <class T>
-STDStream<T>::STDStream(const int ARRAY_SIZE, int device)
-  noexcept : array_size{ARRAY_SIZE}, a{new T[array_size]}, b{new T[array_size]}, c{new T[array_size]}
-{
-}
 
 template <class T>
-STDStream<T>::~STDStream()
+STDStream<T>::STDStream(const int ARRAY_SIZE, int device)
+  noexcept : array_size{ARRAY_SIZE}, range(0, array_size), a(array_size), b(array_size), c(array_size) 
 {
-  delete[] a;
-  delete[] b;
-  delete[] c;
 }
 
 template <class T>
 void STDStream<T>::init_arrays(T initA, T initB, T initC)
 {
-  std::fill(exe_policy, a, a+array_size, initA);
-  std::fill(exe_policy, b, b+array_size, initB);
-  std::fill(exe_policy, c, c+array_size, initC);
+  std::fill(exe_policy, a.begin(), a.end(), initA);
+  std::fill(exe_policy, b.begin(), b.end(), initB);
+  std::fill(exe_policy, c.begin(), c.end(), initC);
 }
 
 template <class T>
 void STDStream<T>::read_arrays(std::vector<T>& h_a, std::vector<T>& h_b, std::vector<T>& h_c)
 {
-  std::copy(exe_policy, a, a+array_size, h_a.data());
-  std::copy(exe_policy, b, b+array_size, h_b.data());
-  std::copy(exe_policy, c, c+array_size, h_c.data());
+  h_a = a;
+  h_b = b;
+  h_c = c;
 }
 
 template <class T>
 void STDStream<T>::copy()
 {
   // c[i] = a[i]
-  std::copy(exe_policy, a, a+array_size, c) ;
+  std::copy(exe_policy, a.begin(), a.end(), c.begin());
 }
 
 template <class T>
 void STDStream<T>::mul()
 {
   //  b[i] = scalar * c[i];
-  std::transform(exe_policy, c, c+array_size, b, [](T ci){ return startScalar*ci; });
+  std::transform(exe_policy, range.begin(), range.end(), b.begin(), [&, scalar = startScalar](int i) {
+    return scalar * c[i];
+  });
 }
 
 template <class T>
 void STDStream<T>::add()
 {
   //  c[i] = a[i] + b[i];
-  std::transform(exe_policy, a, a+array_size, b, c, std::plus<T>());
+  std::transform(exe_policy, range.begin(), range.end(), c.begin(), [&](int i) {
+    return a[i] + b[i];
+  });
 }
 
 template <class T>
 void STDStream<T>::triad()
 {
   //  a[i] = b[i] + scalar * c[i];
-  std::transform(exe_policy, b, b+array_size, c, a, [](T bi, T ci){ return bi+startScalar*ci; });
+  std::transform(exe_policy, range.begin(), range.end(), a.begin(), [&, scalar = startScalar](int i) {
+    return b[i] + scalar * c[i];
+  });
 }
 
 template <class T>
@@ -79,15 +78,17 @@ void STDStream<T>::nstream()
   //  Need to do in two stages with C++11 STL.
   //  1: a[i] += b[i]
   //  2: a[i] += scalar * c[i];
-  std::transform(exe_policy, a, a+array_size, b, a, [](T ai, T bi){ return ai + bi; });
-  std::transform(exe_policy, a, a+array_size, c, a, [](T ai, T ci){ return ai + startScalar*ci; });
+  std::transform(exe_policy, range.begin(), range.end(), a.begin(), [&, scalar = startScalar](int i) {
+    return a[i] + b[i] + scalar * c[i];
+  });
 }
+   
 
 template <class T>
 T STDStream<T>::dot()
 {
   // sum = 0; sum += a[i]*b[i]; return sum;
-  return std::transform_reduce(exe_policy, a, a+array_size, b, 0.0);
+  return std::transform_reduce(exe_policy, a.begin(), a.end(), b.begin(), 0.0);
 }
 
 void listDevices(void)
diff --git a/STDStream.h b/STDStream.h
index 2249812..b50bad1 100644
--- a/STDStream.h
+++ b/STDStream.h
@@ -11,6 +11,33 @@
 
 #define IMPLEMENTATION_STRING "STD"
 
+template <typename N = size_t>
+class ranged {
+  N from, to; 
+public:
+  ranged(N from, N to ): from(from), to(to) {}
+    class iterator {
+      N num;
+    public:
+      using difference_type = N;
+      using value_type = N;
+      using pointer = const N*;
+      using reference = N&;
+      using iterator_category = std::random_access_iterator_tag;
+      explicit iterator(N _num = 0) : num(_num) {}
+      iterator& operator++() { num++; return *this; }
+      iterator operator++(int) { iterator retval = *this; ++(*this); return retval; }
+      bool operator==(iterator other) const { return num == other.num; }
+      bool operator!=(iterator other) const { return *this != other; }
+      reference operator*() const { return num;}
+      difference_type operator-(const iterator &it) const { return num - it.num; }
+      value_type operator[](const difference_type &i) const { return num+i; }
+
+    };
+    iterator begin() { return iterator(from); }
+    iterator end() { return iterator(to >= from? to+1 : to-1); }
+};
+
 template <class T>
 class STDStream : public Stream<T>
 {
@@ -18,14 +45,18 @@ class STDStream : public Stream<T>
     // Size of arrays
     int array_size;
 
+    // induction range
+    ranged<int> range;
+
     // Device side pointers
-    T *a;
-    T *b;
-    T *c;
+    std::vector<T> a;
+    std::vector<T> b;
+    std::vector<T> c;
+
 
   public:
     STDStream(const int, int) noexcept;
-    ~STDStream();
+    ~STDStream() = default;
 
     virtual void copy() override;
     virtual void add() override;