slides

specifelse/1.cpp

@@ -0,0 +1,7 @@
+int func(int x) {
+    if (x > 0) {
+        return 1;
+    } else {
+        return 2;
+    }
+}

specifelse/2.cpp

@@ -0,0 +1,11 @@
+int slow(int x) {
+    if (x > 0) {
+        return 1;
+    } else {
+        return 0;
+    }
+}
+
+int fast(int x) {
+    return (x > 0);
+}

specifelse/3.cpp

@@ -0,0 +1,11 @@
+int slow(int x) {
+    if (x > 0) {
+        return 42;
+    } else {
+        return 32;
+    }
+}
+
+int fast(int x) {
+    return 32 + (x > 0) * 10;
+}

specifelse/4.cpp

@@ -0,0 +1,47 @@
+#include <vector>
+#include <algorithm>
+#include "ticktock.h"
+#include "randint.h"
+
+static int ifelse_clamp(int x) {
+    if (x < 0) {
+        return 0;
+    } else if (x > 255) {
+        return 1;
+    } else {
+        return x;
+    }
+}
+
+static int bailan_clamp(int x) {
+    return (x < 0) ? 0 : ((x > 255) ? 1 : x);
+}
+
+static int addmul_clamp(int x) {
+    return (x >= 0) * (x <= 255) * x + (x > 255);
+}
+
+__attribute__((noinline)) void test(int *a, int n, int (*clamp)(int)) {
+    for (int i = 0; i < n; i++) {
+        a[i] = clamp(a[i]);
+    }
+}
+
+int main() {
+    std::vector<int> a((int)1e7);
+
+    std::generate(a.begin(), a.end(), randint<int, -512, 512>);
+    TICK(ifelse);
+    test(a.data(), a.size(), ifelse_clamp);
+    TOCK(ifelse);
+
+    std::generate(a.begin(), a.end(), randint<int, -512, 512>);
+    TICK(bailan);
+    test(a.data(), a.size(), bailan_clamp);
+    TOCK(bailan);
+
+    std::generate(a.begin(), a.end(), randint<int, -512, 512>);
+    TICK(addmul);
+    test(a.data(), a.size(), addmul_clamp);
+    TOCK(addmul);
+}

specifelse/randint.h

@@ -5,7 +5,13 @@
 template <class T>
 static T randint(T minVal, T maxVal) {
     static std::mt19937 gen(0);
-    std::uniform_int_distribution<char> uni(minVal, maxVal);
+    std::uniform_int_distribution<T> uni(minVal, maxVal);
     return uni(gen);
 }
 
+template <class T, T minVal, T maxVal>
+static T randint() {
+    static std::mt19937 gen(0);
+    std::uniform_int_distribution<T> uni(minVal, maxVal);
+    return uni(gen);
+}