Artemis: Proposed changes for increased performance

src/algorithms/primes.cc

@@ -4,14 +4,17 @@
  *
  *  @param n Number to check
  *  @return True if n is prime, false otherwise
- */
+ */ 
 bool
 Primes::IsPrime(int n) {
-  if (n <= 1) {
+  if (n <= 3) {
+    return n > 1;
+  }
+  if (n % 2 == 0 || n % 3 == 0) {
     return false;
   }
-  for (int i = 2; i < n; i += 1) {
-    if (n % i == 0) {
+  for (int i = 5; i * i <= n; i += 6) {
+    if (n % i == 0 || n % (i + 2) == 0) {
       return false;
     }
   }
@@ -51,4 +54,4 @@ Primes::PrimeFactors(int n) {
     }
   }
   return factors;
-}
+}

src/control/double.cc

@@ -1,3 +1,4 @@
+#include <unordered_map>
 #include "double.h"
 
 /**
@@ -24,14 +25,12 @@ DoubleForLoop::SumSquare(int n) {
  *
  * @param n
  * @return the sum of all triangle numbers from T(1) to T(n)
- */
+ */ 
 long
 DoubleForLoop::SumTriangle(int n) {
   long sum = 0;
-  for (int i = 0; i < n + 1; i += 1) {
-    for (int j = 0; j < i; j += 1) {
-      sum = sum + (long) j;
-    }
+  for (int i = 1; i <= n; ++i) {
+    sum += (long)i * (i - 1) / 2; 
   }
   return sum;
 }
@@ -44,22 +43,20 @@ DoubleForLoop::SumTriangle(int n) {
  *
  * @param v
  * @return the number of pairs in an vay
- */
+ */ 
 int
 DoubleForLoop::CountPairs(std::vector<int> v) {
-  int count = 0;
+  std::unordered_map<int, int> counts;
   for (int i = 0; i < (int) v.size(); i += 1) {
-    int nDuplicates = 0;
-    for (int j = 0; j < (int) v.size(); j += 1) {
-      if (v[i] == v[j]) {
-        nDuplicates += 1;
-      }
-    }
-    if (nDuplicates == 2) {
-      count += 1;
+    counts[v[i]]++;
+  }
+  int nPairs = 0;
+  for (auto it = counts.begin(); it != counts.end(); ++it) {
+    if (it->second == 2) {
+      nPairs++;
     }
   }
-  return count / 2;
+  return nPairs;
 }
 
 /**
@@ -98,4 +95,4 @@ DoubleForLoop::SumMatrix(std::vector<std::vector<int>> matrix) {
     }
   }
   return sum;
-}
+}

src/control/single.cc

@@ -1,20 +1,9 @@
 #include "single.h"
 
-/**
- * @brief Sums all integer values from 0 to n
- *
- * @param n the upper bound (non-inclusive)
- * @return the sum of all integer values from 0 to n
- */
-int
-SingleForLoop::SumRange(int n) {
-  int array[n];
+int SingleForLoop::SumRange(int n) {
   int sum = 0;
   for (int i = 0; i < n; i += 1) {
-    array[i] = i;
-  }
-  for (int i = 0; i < n; i += 1) {
-    sum += array[i];
+    sum += i;
   }
   return sum;
 }
@@ -41,24 +30,12 @@ SingleForLoop::MaxVector(std::vector<int> &arr) {
   return max;
 }
 
-/**
- * @brief Sums all values from 0 to n that are divisible by m
- *
- * @param n the upper bound (non-inclusive)
- * @param m the modulus
- * @return the sum of all values from 0 to n that are divisible by m
- */
-int
-SingleForLoop::SumModulus(int n, int m) {
-  int array[n];
+int SingleForLoop::SumModulus(int n, int m) {
   int sum = 0;
   for (int i = 0; i < n; i += 1) {
-    array[i] = i;
-  }
-  for (int i = 0; i < n; i += 1) {
-    if (array[i] % m == 0) {
-      sum += array[i];
+    if (i % m == 0) {
+      sum += i;
     }
   }
   return sum;
-}
+}

src/datastructures/list.cc

@@ -1,3 +1,4 @@
+#include <algorithm>
 #include "list.h"
 
 /** @brief shuffles a list into a new list
@@ -28,14 +29,12 @@ OpsList::Shuffle(std::list<int> &l) {
  * @param start the start index of the slice
  * @param end the end index of the slice (exclusive)
  * @return a new list with the elements of l sliced
- */
+ */ 
 std::list<int>
 OpsList::Slice(std::list<int> &l, int start, int end) {
   std::list<int> ret;
-  for (int i = start; i < end; i++) {
-    std::list<int>::iterator it = l.begin();
-    std::advance(it, i);
-    ret.push_back(*it);
-  }
+  auto it = std::next(l.begin(), start);
+  auto end_it = std::next(l.begin(), end);
+  ret.insert(ret.end(), it, end_it);
   return ret;
-}
+}

src/datastructures/vector.cc

@@ -1,3 +1,4 @@
+#include <algorithm>
 #include "vector.h"
 
 #include <iostream>
@@ -72,25 +73,10 @@ OpsVector::SearchVector(std::vector<int> &v, int n) {
   return ret;
 }
 
-/**
- * @brief Sorts the vector in ascending order.
- *
- * @param v Vector to sort.
- * @return The sorted vector.
- */
 std::vector<int>
 OpsVector::SortVector(std::vector<int> &v) {
   std::vector<int> ret(v);
-
-  for (int i = 0; i < (int) ret.size(); i += 1) {
-    for (int j = 0; j < (int) ret.size() - 1; j += 1) {
-      if (ret[j] > ret[j + 1]) {
-        int temp = ret[j];
-        ret[j] = ret[j + 1];
-        ret[j + 1] = temp;
-      }
-    }
-  }
+  std::sort(ret.begin(), ret.end());
   return ret;
 }
 
@@ -149,4 +135,4 @@ OpsVector::MergeVectors(std::vector<int> &v1, std::vector<int> &v2) {
   }
 
   return ret;
-}
+}