Make mergesort working

docker/Dockerfile

@@ -3,8 +3,7 @@ FROM ubuntu:${UBUNTU_VERSION}
 
 # Build environment
 # Profiling and analyzer tools
-RUN --mount=type=bind,target=/var/lib/apt \
-    apt-get -y update \
+RUN apt-get -y update \
     && DEBIAN_FRONTEND=noninteractive TZ=Europe/Berlin apt-get -y install tzdata apt-utils \
     && apt-get -y upgrade \
     && apt-get -y install python3 python3-pip lsb-release software-properties-common \

task1/dataset-gen.py

@@ -8,7 +8,7 @@ print("Generated random vector with {} entries".format(randvec.size))
 
 with open("dataset.dat", "w") as file:
     for value in randvec:
-        file.write("{}\n".format(value))
+        file.write(str(value) + '\n')
 
 fsize = os.path.getsize("dataset.dat")
 print("File written down with Size {} MB".format(fsize/1000/1000))

task1/main.cpp

@@ -1,7 +1,6 @@
 #include <fmt/format.h>
-#include <QCoreApplication>
-#include <QFile>
 #include <vector>
+#include <fstream>
 
 #include <mergesort.h>
 
@@ -22,40 +21,48 @@ your predictions and their graphical illustration?
 */
 
 int main(int argc, char *argv[]) {
-    QFile file("dataset.dat");
-    if(!file.open(QIODevice::ReadOnly | QIODevice::Text)) {
-        fmt::print("Could not open file");
-       return 0;
-    }
+    try {
+        std::ifstream file("dataset.dat", std::ios_base::in);
 
-    fmt::print("Opened file {} sucessfully!\n", file.fileName().toStdString());
+        fmt::print("Opened file {} sucessfully!\n", "dummy");
 
+        std::vector<int32_t> dataset{10, 3, 244, 23, 293, 2393, 302};
 
-    std::vector<int32_t> dataset;
-    int counter = 0;
-
-    while(!file.atEnd()) {
-        dataset.emplace_back(file.readLine().toInt());
-    }
-
-    fmt::print("Read {} values from {}\n", dataset.size(), file.fileName().toStdString());
+//        std::vector<int32_t> dataset;
+//        int counter = 0;
+//
+//        while(!file.eof()) {
+//            int32_t buf;
+//            file >> buf;
+//            dataset.emplace_back(buf);
+//        }
+//
+//        fmt::print("Read {} values from {}\n", dataset.size(), "dummy");
 
         algo::mergesort(dataset.begin(), dataset.end(), [](int32_t a, int32_t b) {
             return (a>b);
         });
 
-    QFile outfile("dataset-sorted.dat");
-    if(!outfile.open(QIODevice::WriteOnly | QIODevice::Text)) {
-        fmt::print("Error! Could not create output file");
-    }
+        fmt::print("sorted");
 
-    for(auto &val : dataset) {
-        outfile.write(fmt::format("{}\n", val).c_str());
-    }
-
-    file.close();
-    outfile.flush();
-    outfile.close();
+//        QFile outfile("dataset-sorted.dat");
+//        if(!outfile.open(QIODevice::WriteOnly | QIODevice::Text)) {
+//            fmt::print("Error! Could not create output file");
+//        }
+//
+//        for(auto &val : dataset) {
+//            outfile.write(fmt::format("{}\n", val).c_str());
+//        }
+//
+//        file.close();
+//        outfile.flush();
+//        outfile.close();
 
         return 0;
+
+    } catch (std::exception e) {
+        fmt::print("Could not open file");
+        return -1;
+    }
+
 }

task1/mergesort.h

@@ -8,6 +8,7 @@ namespace algo {
     template<typename Iterator, typename Comparator>
     void merge(Iterator start, Iterator middle, Iterator end, Comparator cmp, Iterator output_start) {
         Iterator start_m = start;
+        Iterator begin = output_start;
         Iterator start2 = middle + 1;
 
         //merge from input until one half completes
@@ -35,37 +36,40 @@ namespace algo {
             output_start++;
         }
 
-        const auto nit = std::distance(start_m, end);
-        for (auto i = 0; i <= nit; i++, start_m++, output_start++) {
-            *start_m = *output_start;
+        const auto size = std::distance(start_m, end);
+        for (auto i = 0; i <= size; i++, start_m++, begin++) {
+            *start_m = *begin;
         }
 
     }
 
     template<typename Container, typename Iterator, typename Comparator>
-    void mergesort_splitup(Container &output_vec, Iterator start, Iterator end, Comparator cmp, Iterator output_start) {
-        Iterator middle = start;
-        Iterator output_started_from = output_start;
+    void ms_split(Container &output_vec, Iterator start, Iterator end, Comparator cmp, Iterator output_start) {
+        Iterator mid = start;
+        Iterator begin = output_start;
 
-        //move middle iterator litterally to the middle
-        std::advance(middle, std::distance(start, end) / 2);
+        if (std::distance(start, end) < 1) {
+            return;
+        } else {
+            //move mid iterator litterally to the mid
+            std::advance(mid, std::distance(start, end) / 2);
             //sort the first half within an recursion
-        mergesort_splitup(output_vec, start, middle, cmp, output_start);
+            ms_split(output_vec, start, mid, cmp, output_start);
 
             //move output iterator
-        std::advance(output_start, std::distance(start, middle + 1));
+            std::advance(output_start, std::distance(start, mid + 1));
             //sort the second half within a recursion
-        mergesort_splitup(output_vec, middle + 1, end, cmp, output_start);
+            ms_split(output_vec, mid + 1, end, cmp, output_start);
 
             //merge everything together starting from the complete beginning
-        merge(start, middle, end, cmp, output_started_from);
+            merge(start, mid, end, cmp, begin);
+        }
     }
 
     template<typename Iterator, typename Comparator>
     void mergesort(Iterator start, Iterator end, Comparator cmp) {
         using valtype = typename std::iterator_traits<Iterator>::value_type;
-
-        std::vector<valtype> output_vec(std::distance(start, end));
-
+        std::vector<valtype> temporary_dataset(std::distance(start, end));
+        ms_split(temporary_dataset, start, end - 1, cmp, temporary_dataset.begin());
     }
 }