From cd742751ed9d1d004d45a5307d60e49aee68ad0a Mon Sep 17 00:00:00 2001
From: robtor <robtor2000@web.de>
Date: Fri, 3 Nov 2023 09:03:36 +0100
Subject: [PATCH] mobile optimization

---
 task1/main.cpp    | 11 ++++++-----
 task1/mergesort.h | 16 ++++++++--------
 2 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/task1/main.cpp b/task1/main.cpp
index 0a01ede..72c0ee3 100644
--- a/task1/main.cpp
+++ b/task1/main.cpp
@@ -54,24 +54,25 @@ auto main(int argc, char *argv[]) -> int {
         auto dataset_seq = dataset;
 
         auto t1 = std::chrono::high_resolution_clock::now();
-        algo::MergeSort_v1::sort(dataset_seq.begin(), dataset_seq.end(), [](int32_t a, int32_t b) {
+        algo::MergeSort_mt::sort(dataset_seq, [](int32_t a, int32_t b) {
             return (a > b);
-        });
+        }, 0);
         auto t2 = std::chrono::high_resolution_clock::now();
 
         auto delay_ms = std::chrono::duration_cast<std::chrono::milliseconds>(t2 - t1);
         fmt::print("Sorted {} entries within {} ms in sequential\n", dataset_seq.size(), delay_ms.count());
 
 
-        const int nthreads = std::thread::hardware_concurrency();
+        //const int max_depth = std::thread::hardware_concurrency();
+        const int max_depth = 4;
         t1 = std::chrono::high_resolution_clock::now();
         algo::MergeSort_mt::sort(dataset_par, [](int32_t a, int32_t b) {
             return (a > b);
-        }, nthreads);
+        }, max_depth);
         t2 = std::chrono::high_resolution_clock::now();
 
         delay_ms = std::chrono::duration_cast<std::chrono::milliseconds>(t2 - t1);
-        fmt::print("Sorted {} entries within {} ms in parallel using {} threads\n", dataset_seq.size(), delay_ms.count(), nthreads);
+        fmt::print("Sorted {} entries within {} ms in parallel using {} threads\n", dataset_seq.size(), delay_ms.count(), max_depth);
 
         auto eq = (dataset_seq == dataset_par);
         fmt::print("Equality: {}\n", eq);
diff --git a/task1/mergesort.h b/task1/mergesort.h
index c2aa7af..b5ad3eb 100644
--- a/task1/mergesort.h
+++ b/task1/mergesort.h
@@ -327,7 +327,7 @@ namespace algo {
         }
 
         template<typename T, typename Comparator>
-        static auto split(std::vector<T> data, Comparator cmp, int depth, int &num_threads,
+        static auto split(std::vector<T> data, Comparator cmp, int depth, int &max_depth,
                           std::mutex &mut) -> std::vector<T>{
 
             if (data.size() <= 1) {
@@ -350,15 +350,15 @@ namespace algo {
             std::vector<T> left(data.begin(), mid);
             std::vector<T> right(mid, data.end());
 
-            if (depth < num_threads) {
-                std::thread left_thread([&]() { left = split(left,  cmp, depth + 1, num_threads, mut); });
-                std::thread right_thread([&]() { right = split(right,  cmp, depth + 1, num_threads, mut); });
+            if (depth < max_depth) {
+                std::thread left_thread([&]() { left = split(left, cmp, depth + 1, max_depth, mut); });
+                std::thread right_thread([&]() { right = split(right, cmp, depth + 1, max_depth, mut); });
 
                 left_thread.join();
                 right_thread.join();
             } else {
-                left = split(left,  cmp, depth + 1, num_threads, mut);
-                right = split(right,  cmp, depth + 1, num_threads, mut);
+                left = split(left, cmp, depth + 1, max_depth, mut);
+                right = split(right, cmp, depth + 1, max_depth, mut);
             }
 
             return merge(left, right, cmp, mut);
@@ -367,12 +367,12 @@ namespace algo {
     public:
         template<typename T, typename Comparator>
         static auto
-        sort(std::vector<T> &data, Comparator cmp, int num_threads = std::thread::hardware_concurrency()) -> void {
+        sort(std::vector<T> &data, Comparator cmp, int max_depth = 0) -> void {
             std::mutex local_result_lock;
             std::vector<T> output;
             output.reserve(data.size());
 
-            output = split(data, cmp, 0, num_threads, local_result_lock);
+            output = split(data, cmp, 0, max_depth, local_result_lock);
             data.assign(output.begin(), output.end());
         }
     };