From cf26418e28d82ed3bf8f66d76f2ab8e33c6fc060 Mon Sep 17 00:00:00 2001
From: Henrique Bucher <hbucher@gmail.com>
Date: Wed, 6 Mar 2024 13:46:18 -0600
Subject: [PATCH 1/2] Make nsieve fair. Solves #419

---
 bench/algorithm/nsieve/3.cpp | 46 ++++++++++++++++++++++++++++++++++++
 bench/bench_cpp.yaml         |  1 +
 2 files changed, 47 insertions(+)
 create mode 100644 bench/algorithm/nsieve/3.cpp

diff --git a/bench/algorithm/nsieve/3.cpp b/bench/algorithm/nsieve/3.cpp
new file mode 100644
index 00000000..6eb45b56
--- /dev/null
+++ b/bench/algorithm/nsieve/3.cpp
@@ -0,0 +1,46 @@
+
+// The Computer Language Shootout
+// http://shootout.alioth.debian.org/
+// Precedent C entry modified by bearophile for speed and size, 31 Jan 2006
+// Converted to C++ by Paul Kitchin
+
+#include <iomanip>
+#include <iostream>
+#include <sstream>
+#include <vector>
+
+void nsieve(std::size_t max) {
+  std::vector<bool> flags(max,false);
+  std::size_t count = 0;
+  for (std::size_t value = 2; value < max; ++value) {
+    if (!flags[value]) {
+      ++count;
+      for (std::size_t multiple = value * 2; multiple < max;
+           multiple += value) {
+        flags[multiple] = true;
+      }
+    }
+  }
+  std::cout << "Primes up to " << std::setw(8) << max << ' ' << std::setw(8)
+            << count << '\n';
+}
+
+int main(int argc, char **argv) {
+  if (argc != 2) {
+    std::cerr << "usage: " << argv[0] << " <n>\n";
+    return 1;
+  }
+  unsigned int count;
+  {
+    std::istringstream convertor(argv[1]);
+    if (!(convertor >> count) || !convertor.eof()) {
+      std::cerr << "usage: " << argv[0] << " <n>\n";
+      std::cerr << "\tn must be an integer\n";
+      return 1;
+    }
+  }
+  for (std::size_t i = 0; i < 3; ++i) {
+    nsieve(10000 << (count - i));
+  }
+}
+
diff --git a/bench/bench_cpp.yaml b/bench/bench_cpp.yaml
index e17d7c0a..424195b5 100644
--- a/bench/bench_cpp.yaml
+++ b/bench/bench_cpp.yaml
@@ -18,6 +18,7 @@ problems:
   - name: nsieve
     source:
       - 1.cpp
+      - 3.cpp
 compiler_version_command:
 compiler_version_regex:
 runtime_version_parameter:

From 4ff8324be85c9597f4e2f518570023d92d1c9367 Mon Sep 17 00:00:00 2001
From: Henrique Bucher <hbucher@gmail.com>
Date: Wed, 6 Mar 2024 13:48:23 -0600
Subject: [PATCH 2/2] Replaced wrong version.

---
 bench/algorithm/nsieve/3.cpp | 50 +++++++++++++++---------------------
 1 file changed, 20 insertions(+), 30 deletions(-)

diff --git a/bench/algorithm/nsieve/3.cpp b/bench/algorithm/nsieve/3.cpp
index 6eb45b56..910e1064 100644
--- a/bench/algorithm/nsieve/3.cpp
+++ b/bench/algorithm/nsieve/3.cpp
@@ -1,4 +1,3 @@
-
 // The Computer Language Shootout
 // http://shootout.alioth.debian.org/
 // Precedent C entry modified by bearophile for speed and size, 31 Jan 2006
@@ -9,38 +8,29 @@
 #include <sstream>
 #include <vector>
 
-void nsieve(std::size_t max) {
-  std::vector<bool> flags(max,false);
-  std::size_t count = 0;
-  for (std::size_t value = 2; value < max; ++value) {
-    if (!flags[value]) {
-      ++count;
-      for (std::size_t multiple = value * 2; multiple < max;
-           multiple += value) {
-        flags[multiple] = true;
-      }
+#include <iostream>
+#include <cmath>
+#include <vector>
+#include <algorithm>
+
+inline void nsieve(unsigned int limit) {
+    std::vector<bool> primes(limit + 1, true);
+    primes[1] = false;
+    unsigned int p = 2;
+    while (p <= static_cast<unsigned int>(std::sqrt(limit))) {
+        for (unsigned int i = p * p; i <= limit; i += p) {
+            primes[i] = false;
+        }
+        p = std::find(primes.begin() + p + 1, primes.end(), true) - primes.begin();
     }
-  }
-  std::cout << "Primes up to " << std::setw(8) << max << ' ' << std::setw(8)
-            << count << '\n';
+    unsigned int primeCount = std::count(primes.begin(), primes.end(), true);
+    std::cout << "Primes up to " << std::setw(8) << limit << std::setw(9) << primeCount << '\n';
 }
 
 int main(int argc, char **argv) {
-  if (argc != 2) {
-    std::cerr << "usage: " << argv[0] << " <n>\n";
-    return 1;
-  }
-  unsigned int count;
-  {
-    std::istringstream convertor(argv[1]);
-    if (!(convertor >> count) || !convertor.eof()) {
-      std::cerr << "usage: " << argv[0] << " <n>\n";
-      std::cerr << "\tn must be an integer\n";
-      return 1;
+    unsigned int n = (argc <= 1) ? 4 : std::atoi(argv[1]);
+    for (unsigned int i = n; i >= n - 2; --i) {
+        nsieve(10000 << i);
     }
-  }
-  for (std::size_t i = 0; i < 3; ++i) {
-    nsieve(10000 << (count - i));
-  }
+    return 0;
 }
-