fixes divide by zero in mask.

eval.py

@@ -8,7 +8,8 @@ from pathlib import Path
 def run_experiment(output_file, build_dir):
     # The number of threads is not currently used, it's just here in case you want to parallelize your code.
     for threads in [1]:
-        for size in [1e2, 1e3, 1e4 + 1, 1e5, 1e6 - 1, 1e7]:
+        # for size in [1e2, 1e3, 1e4 + 1, 1e5, 1e6 - 1, 1e7]:
+        for size in [1e2]:
             print("Measuring p=" + str(threads) + " n=" + str(size))
             executable = Path(build_dir) / "Sorter"
             returncode = subprocess.call([executable, str(size), str(threads)], stdout=output_file)

src/sorter.cpp

@@ -4,6 +4,8 @@
 #include <iterator>
 #include <cassert>
 #include <iostream>
+#include <bitset>
+#include <climits>
 
 namespace ae {
 
@@ -21,46 +23,49 @@ void sorter::msd_inplace_radix_sort(
   size_t passes, 
   const std::function<void(std::span<container::element_type> bucket)>& bucket_sort
 ) {
-    std::cerr << "passes: " << passes << std::endl;
+  std::cerr << "passes: " << passes << "size: " << range.size() << std::endl;
   if (sorter::RADIX_ITERATIONS == passes) {
-    bucket_sort(range);
+    std::cerr << "going to robin " << *std::begin(range) << std::endl;
+    if (std::begin(range) + 1 < std::end(range)) {
+      bucket_sort(range);
+    }
     return;
   }
 
   auto lower = std::begin(range);
   auto upper = std::end(range);
 
-  for (auto element = lower; element < std::end(range);) {
+  for (auto element = lower; element < upper;) {
     std::cerr << *element << " " << &*element << " " << &*lower << " " << &*upper << std::endl;
     // Mask out the <sorter::RADIX_ITERATIONS>-last bit and check if it is set
-    if ((*element & (1uz << sizeof(container::element_type) * 8 - passes))) {
+    // std::cerr << std::bitset<64>((1L << (sizeof(container::element_type) * CHAR_BIT - passes - 1))) << std::endl;
+    // fprintf(stderr, "%lx\n", (1L << (sizeof(container::element_type) * CHAR_BIT - passes - 1)));
+    if ((*element & (1L << (sizeof(container::element_type) * CHAR_BIT - passes - 1)))) {
       // The <passes> bit is set, so move to the beginning of the end section and decrement the upper iterator
-      std::swap(upper, element);
+      std::swap(*upper, *element);
       --upper;
     } else {
       // The <passes> bit is unset, so move to the end of the beginning section and increment the upper iterator
-      std::swap(lower, element);
+      std::swap(*lower, *element);
       ++lower;
-    }
-    if (element < lower) {
       ++element;
-    } else if (element > upper) {
-      --element;
     }
   }
-  assert(lower == upper);
+  // assert(lower == upper);
   sorter::msd_inplace_radix_sort(std::span<container::element_type> (std::begin(range), lower), passes + 1, bucket_sort);
   sorter::msd_inplace_radix_sort(std::span<container::element_type> (upper, std::end(range)), passes + 1, bucket_sort);
 }
-
 void sorter::robin_hood_sort(std::span<container::element_type> bucket) {
+  std::cerr << "robin hood lol" << std::endl;
   const auto size = bucket.size() + sorter::OVERHEAD_SIZE;
-  const size_t mask = ~(-1 >> sorter::RADIX_ITERATIONS);
+  const auto mask = ((1L) << (sizeof(container::element_type) * CHAR_BIT - sorter::RADIX_ITERATIONS)) - 1;
   container::element_type space[size];
-
+  std::cerr << "robin hood before loop" << std::endl;
   for (auto element : bucket) {
     auto masked_element = (element & mask);
-    auto index = masked_element * size/ mask;
+    std::cerr << "robin hood elements " << element << " " << masked_element << " " << size << " " << mask << std::endl;
+    auto index = (masked_element * size) / mask;
+    std::cerr << "robin hood index " << index << " " << size << std::endl;
     if (space[index] == -1) {
       space[index] = masked_element;
     } else {
@@ -69,6 +74,7 @@ void sorter::robin_hood_sort(std::span<container::element_type> bucket) {
       space[i] = masked_element;
     }
   }
+  std::cerr << "robin hood after loop" << std::endl;
 
   // One final pass to correct linear probing errors
   for (auto i = 1; i < size; ++i) {

src/sorter.hpp

@@ -16,8 +16,8 @@ class sorter {
     const std::function<void(std::span<container::element_type> bucket)>& bucket_sort
   );
 
-  const size_t OVERHEAD_SIZE = 100L;
-  const size_t RADIX_ITERATIONS = 32;
+  const uint32_t OVERHEAD_SIZE = 10L;
+  const uint32_t RADIX_ITERATIONS = 6;
 
   void robin_hood_sort(std::span<container::element_type> range);
 };