Remove vector of indices and use a lazy iota range instead (#838)

* Create lazy range

* Formatting

* Use lazy iota

src/include/migraphx/iota_iterator.hpp

@@ -2,14 +2,15 @@
 #define MIGRAPHX_GUARD_RTGLIB_IOTA_ITERATOR_HPP
 
 #include <migraphx/config.hpp>
+#include <migraphx/functional.hpp>
 #include <iterator>
 #include <type_traits>
 
 namespace migraphx {
 inline namespace MIGRAPHX_INLINE_NS {
 
-template <class F, class Iterator = std::size_t>
-struct iota_iterator
+template <class F, class Iterator = std::ptrdiff_t>
+struct basic_iota_iterator
 {
     Iterator index;
     F f;
@@ -20,40 +21,40 @@ struct iota_iterator
     using pointer           = typename std::add_pointer<value_type>::type;
     using iterator_category = std::random_access_iterator_tag;
 
-    iota_iterator& operator+=(int n)
+    basic_iota_iterator& operator+=(int n)
     {
         index += n;
         return *this;
     }
 
-    iota_iterator& operator-=(int n)
+    basic_iota_iterator& operator-=(int n)
     {
         index -= n;
         return *this;
     }
 
-    iota_iterator& operator++()
+    basic_iota_iterator& operator++()
     {
         index++;
         return *this;
     }
 
-    iota_iterator& operator--()
+    basic_iota_iterator& operator--()
     {
         index--;
         return *this;
     }
 
-    iota_iterator operator++(int) // NOLINT
+    basic_iota_iterator operator++(int) // NOLINT
     {
-        iota_iterator it = *this;
+        basic_iota_iterator it = *this;
         index++;
         return it;
     }
 
-    iota_iterator operator--(int) // NOLINT
+    basic_iota_iterator operator--(int) // NOLINT
     {
-        iota_iterator it = *this;
+        basic_iota_iterator it = *this;
         index--;
         return it;
     }
@@ -61,55 +62,71 @@ struct iota_iterator
     reference operator*() const { return f(index); }
 };
 
+template <class T, class F>
+inline basic_iota_iterator<F, T> make_basic_iota_iterator(T x, F f)
+{
+    return basic_iota_iterator<F, T>{x, f};
+}
+
+template <class F, class Iterator>
+inline basic_iota_iterator<F, Iterator> operator+(basic_iota_iterator<F, Iterator> x,
+                                                  std::ptrdiff_t y)
+{
+    return x += y;
+}
+
 template <class F, class Iterator>
-inline iota_iterator<F, Iterator> operator+(iota_iterator<F, Iterator> x,
-                                            iota_iterator<F, Iterator> y)
+inline basic_iota_iterator<F, Iterator> operator+(std::ptrdiff_t x,
+                                                  basic_iota_iterator<F, Iterator> y)
 {
-    return iota_iterator<F, Iterator>(x.index + y.index, x.f);
+    return y + x;
 }
 
 template <class F, class Iterator>
-inline std::ptrdiff_t operator-(iota_iterator<F, Iterator> x, iota_iterator<F, Iterator> y)
+inline std::ptrdiff_t operator-(basic_iota_iterator<F, Iterator> x,
+                                basic_iota_iterator<F, Iterator> y)
 {
     return x.index - y.index;
 }
 
 template <class F, class Iterator>
-inline bool operator==(iota_iterator<F, Iterator> x, iota_iterator<F, Iterator> y)
+inline bool operator==(basic_iota_iterator<F, Iterator> x, basic_iota_iterator<F, Iterator> y)
 {
     return x.index == y.index;
 }
 
 template <class F, class Iterator>
-inline bool operator!=(iota_iterator<F, Iterator> x, iota_iterator<F, Iterator> y)
+inline bool operator!=(basic_iota_iterator<F, Iterator> x, basic_iota_iterator<F, Iterator> y)
 {
     return x.index != y.index;
 }
 
 template <class F, class Iterator>
-inline bool operator<(iota_iterator<F, Iterator> x, iota_iterator<F, Iterator> y)
+inline bool operator<(basic_iota_iterator<F, Iterator> x, basic_iota_iterator<F, Iterator> y)
 {
     return x.index < y.index;
 }
 
 template <class F, class Iterator>
-inline bool operator>(iota_iterator<F, Iterator> x, iota_iterator<F, Iterator> y)
+inline bool operator>(basic_iota_iterator<F, Iterator> x, basic_iota_iterator<F, Iterator> y)
 {
     return x.index > y.index;
 }
 
 template <class F, class Iterator>
-inline bool operator>=(iota_iterator<F, Iterator> x, iota_iterator<F, Iterator> y)
+inline bool operator>=(basic_iota_iterator<F, Iterator> x, basic_iota_iterator<F, Iterator> y)
 {
     return x.index >= y.index;
 }
 
 template <class F, class Iterator>
-inline bool operator<=(iota_iterator<F, Iterator> x, iota_iterator<F, Iterator> y)
+inline bool operator<=(basic_iota_iterator<F, Iterator> x, basic_iota_iterator<F, Iterator> y)
 {
     return x.index <= y.index;
 }
 
+using iota_iterator = basic_iota_iterator<id>;
+
 } // namespace MIGRAPHX_INLINE_NS
 } // namespace migraphx
 

src/include/migraphx/ranges.hpp

@@ -5,6 +5,7 @@
 #include <vector>
 #include <initializer_list>
 #include <migraphx/rank.hpp>
+#include <migraphx/iota_iterator.hpp>
 #include <migraphx/type_name.hpp>
 #include <migraphx/errors.hpp>
 #include <migraphx/requires.hpp>
@@ -208,12 +209,18 @@ struct iterator_range
     Iterator end() const { return last; }
 };
 
-template <class Iterator>
+template <class Iterator, MIGRAPHX_REQUIRES(not std::is_integral<Iterator>{})>
 iterator_range<Iterator> range(Iterator start, Iterator last)
 {
     return {start, last};
 }
 
+inline iterator_range<iota_iterator> range(std::ptrdiff_t start, std::ptrdiff_t last)
+{
+    return {{start, {}}, {last, {}}};
+}
+inline iterator_range<iota_iterator> range(std::ptrdiff_t last) { return range(0, last); }
+
 template <class Iterator>
 iterator_range<Iterator> range(std::pair<Iterator, Iterator> p)
 {

src/include/migraphx/tensor_view.hpp

@@ -36,8 +36,9 @@ template <class T>
 struct tensor_view
 {
     using value_type = T;
-    using iterator       = iota_iterator<tensor_view_iterator_read<tensor_view<T>>>;
-    using const_iterator = iota_iterator<tensor_view_iterator_read<const tensor_view<T>>>;
+    using iterator   = basic_iota_iterator<tensor_view_iterator_read<tensor_view<T>>, std::size_t>;
+    using const_iterator =
+        basic_iota_iterator<tensor_view_iterator_read<const tensor_view<T>>, std::size_t>;
     tensor_view() : m_data(nullptr) {}
     tensor_view(shape s, T* d) : m_data(d), m_shape(std::move(s)) {}
 

src/simplify_reshapes.cpp

@@ -376,9 +376,7 @@ struct find_resize
             return;
         }
         arg_ind.visit([&](auto v) { vec_ind.assign(v.begin(), v.end()); });
-        std::vector<int> index(out_shape.elements());
-        std::iota(index.begin(), index.end(), 0);
-        if(not std::all_of(index.begin(), index.end(), [&](auto i) {
+        if(not all_of(range(out_shape.elements()), [&](auto i) {
                auto out_idx = out_shape.multi(i);
                auto in_idx  = out_idx;
                std::transform(out_idx.begin(),