alternate input during non-compared runs, to catch non-reset state in leven::compute

asgn/fmwkng.hpp

@@ -1339,7 +1339,7 @@ namespace fmwkng {
 		private:
 			using self_ = index_iterator<index_t>;
 		public:
-			using iterator_category = std::input_iterator_tag;
+			using iterator_category = std::bidirectional_iterator_tag;
 			using value_type = index_t;
 			using difference_type = std::make_signed_t<index_t>;
 			using pointer = const index_t*;
@@ -1358,6 +1358,15 @@ namespace fmwkng {
 			{
 				return self_(v_++);
 			}
+			self_& operator--()
+			{
+				--v_;
+				return *this;
+			}
+			self_ operator--(int)
+			{
+				return self_(v_--);
+			}
 			bool operator==(const self_& b) const
 			{
 				return v_ == b.v_;

asgn/levenasgn.hpp

@@ -90,6 +90,68 @@ namespace levenasgn {
 		}
 	};
 
+	struct generator_4_alt {
+
+		auto begin1() const
+		{
+			return v1_.cbegin();
+		}
+
+		auto end1() const
+		{
+			return v1_.cend();
+		}
+
+		auto data1() const
+		{
+			return v1_.data();
+		}
+
+		auto size1() const
+		{
+			return v1_.size();
+		}
+
+		auto data2() const
+		{
+			return v2_.data();
+		}
+
+		auto size2() const
+		{
+			return v2_.size();
+		}
+
+		auto begin2() const
+		{
+			return v2_.cbegin();
+		}
+
+		auto end2() const
+		{
+			return v2_.cend();
+		}
+
+		template< typename GP>
+		generator_4_alt(GP&& p, std::size_t s1, std::size_t s2)
+			: s2_(s2),
+			s1_(s1),
+			v1_(s1),
+			v2_(s2)
+		{
+			auto gen = [&p]() -> data_element {
+				return p.get();
+			};
+
+			std::generate(v2_.begin(), v2_.end(), gen);
+			std::generate(v1_.begin(), v1_.end(), gen);
+		}
+
+	private:
+		std::size_t s1_, s2_;
+		std::vector< data_element> v1_, v2_;
+	};
+
 	struct policy_random {
 
 		static std::string name() { return "random"; }

asgn/levenmain.cpp

@@ -22,7 +22,11 @@ namespace levenmain {
 						levenasgn::policy_random(
 							std::mt19937_64::default_seed + ctx2.thread_index()
 						), get<a_size>(ctx4), get<b_size>(ctx4));
-
+					levenasgn::generator_4_alt mg_alt(
+						levenasgn::policy_random(
+							std::mt19937_64::default_seed + ctx2.thread_index() + 729
+						), get<a_size>(ctx4), get<b_size>(ctx4));
+					
 					if constexpr ( std::is_constructible_v<levensol::levenstein<policy>, const levenasgn::data_element *, const levenasgn::data_element *, const levenasgn::data_element *, const levenasgn::data_element *> )
 					{
 						// old-style interface
@@ -50,9 +54,14 @@ namespace levenmain {
 						for (auto&& ctx5 : auto_measurement<repeat_policy>(ctx4, 1024))
 						{
 							std::size_t h = 0;
-							for (auto i : for_index<repeats>(ctx5))
+							auto range = for_index<repeats>(ctx5);
+							auto back = *std::prev(range.end());
+							for (auto i : range)
 							{
-								auto rv = data.compute(mg.data1(), mg.data2());
+								auto alt = i != back;
+								auto rv = data.compute(
+									alt ? mg_alt.data1() : mg.data1(), 
+									alt ? mg_alt.data2() : mg.data2());
 								h = rv;
 							}
 							if (stop_for_results(ctx5))