Minor shift changes

bkille · Jun 5, 2024 · 69dc3e9 · 69dc3e9
1 parent 2e47baa
commit 69dc3e9
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Showing 2 changed files with 18 additions and 15 deletions.
diff --git a/benchmark/src/shift_bench.hpp b/benchmark/src/shift_bench.hpp
@@ -16,7 +16,7 @@ auto BM_BitShiftLeft = [](benchmark::State& state, auto input) {
     container_type bitcont = make_random_container<container_type>(container_size); 
     auto first = bit::bit_iterator<decltype(std::begin(bitcont))>(std::begin(bitcont));
     auto last = bit::bit_iterator<decltype(std::end(bitcont))>(std::end(bitcont));
-    auto n = bit::distance(first, last) / 2 - 1;
+    auto n = total_bits / 2 - 1;
     for (auto _ : state) {
         benchmark::DoNotOptimize(bit::shift_left(first, last, n));
         benchmark::ClobberMemory();
@@ -34,7 +34,7 @@ auto BM_BitShiftLeft_UU = [](benchmark::State& state, auto input) {
     container_type bitcont = make_random_container<container_type>(container_size); 
     bit::bit_iterator<iterator_type> first = bit::bit_iterator<iterator_type>(bitcont.begin()) + 1;
     bit::bit_iterator<iterator_type> last = bit::bit_iterator<iterator_type>(bitcont.end()) - 1;
-    auto n = bit::distance(first, last) / 2 + 6;
+    auto n = total_bits / 2 + 3;
     for (auto _ : state) {
         benchmark::DoNotOptimize(bit::shift_left(first, last, n));
         benchmark::ClobberMemory();
@@ -75,7 +75,7 @@ auto BM_BoolShiftLeft = [](benchmark::State& state, auto input) {
     container_type cont = make_random_container<container_type>(container_size); 
     auto first = cont.begin();
     auto last = cont.end();
-    auto n = std::distance(first, last) / 2 + 6;
+    auto n = std::distance(first, last) / 2 - 1;
     for (auto _ : state) {
         benchmark::DoNotOptimize(bit::word_shift_left(first, last, n));
         benchmark::ClobberMemory();
@@ -91,7 +91,7 @@ auto BM_BitShiftRight = [](benchmark::State& state, auto input) {
     container_type bitcont = make_random_container<container_type>(container_size); 
     auto first = bit::bit_iterator<decltype(std::begin(bitcont))>(std::begin(bitcont));
     auto last = bit::bit_iterator<decltype(std::end(bitcont))>(std::end(bitcont));
-    auto n = bit::distance(first, last) / 2 - 1;
+    auto n = total_bits / 2 - 1;
     for (auto _ : state) {
         benchmark::DoNotOptimize(bit::shift_right(first, last, n));
         benchmark::ClobberMemory();
@@ -105,9 +105,9 @@ auto BM_BitShiftRight_UU = [](benchmark::State& state, auto input) {
     auto digits = bit::binary_digits<word_type>::value;
     auto container_size = ceil(float(total_bits) / digits);
     container_type bitcont = make_random_container<container_type>(container_size); 
-    auto first = bit::bit_iterator<decltype(std::begin(bitcont))>(std::begin(bitcont)) + 2;
-    auto last = bit::bit_iterator<decltype(std::end(bitcont))>(std::end(bitcont)) - 3;
-    auto n = bit::distance(first, last) / 2 + 6;
+    auto first = bit::bit_iterator<decltype(std::begin(bitcont))>(std::begin(bitcont)) + 1;
+    auto last = bit::bit_iterator<decltype(std::end(bitcont))>(std::end(bitcont)) - 1;
+    auto n = total_bits / 2 + 3;
     for (auto _ : state) {
         benchmark::DoNotOptimize(bit::shift_right(first, last, n));
         benchmark::ClobberMemory();
@@ -147,7 +147,7 @@ auto BM_BoolShiftRight = [](benchmark::State& state, auto input) {
     container_type cont = make_random_container<container_type>(container_size); 
     auto first = cont.begin();
     auto last = cont.end();
-    auto n = std::distance(first, last) / 2 + 6;
+    auto n = std::distance(first, last) / 2 - 1;
     for (auto _ : state) {
         benchmark::DoNotOptimize(bit::word_shift_right(first, last, n));
         benchmark::ClobberMemory();

diff --git a/include/bitlib/bit-algorithms/shift.hpp b/include/bitlib/bit-algorithms/shift.hpp
@@ -88,19 +88,15 @@ bit_iterator<RandomAccessIt> shift_left(
                 first.position(),
                 (is_last_aligned ? digits : last.position()) - first.position()
         );
-        return bit_iterator<RandomAccessIt>(
-                first.base(),
-                first.position() + d - n
-        );
+        return first + d - n;
     }
 
     // Triggered if all remaining bits can fit in a word
     if (d - n <= digits)
     {
         word_type new_word = get_word<word_type, RandomAccessIt>(middle, d - n);
         write_word<word_type, RandomAccessIt>(new_word, first, d - n);
-        first += d - n;
-        return first;
+        return first + d - n;
     }
     // Multiple word case
     word_type first_value = *first.base();
@@ -349,7 +345,14 @@ bit_iterator<RandomAccessIt> shift_right(
         auto last_base_prev   = std::prev(last.base());
         auto middle_base_prev = std::prev(middle.base());
 
-        while (middle_base_prev + (first.position() <= middle.position())  > first.base()) {
+        while (middle_base_prev > first.base()) {
+            *last_base_prev = _shrd<word_type>(*middle_base_prev, *std::next(middle_base_prev), offset);
+            last_base_prev--;
+            middle_base_prev--;
+        }
+
+        if (first.position() <= middle.position())
+        {
             *last_base_prev = _shrd<word_type>(*middle_base_prev, *std::next(middle_base_prev), offset);
             last_base_prev--;
             middle_base_prev--;