Merge pull request #21 from DoctorLai/pi

Simple PI example

Author: doctorlai-msrc

README.md

@@ -36,6 +36,7 @@ Examples include (and will expand to):
         * [rot47](./rot47/)
     * [prefix-sum](./prefix-sum/)
     * [pi-monte-carlo](./pi-monte-carlo/)
+    * [pi](./pi)
 * Data Structures
     * [map-with-unknown-key](./map-with-unknown-key/)
 * OOP

pi/Makefile

@@ -0,0 +1,30 @@
+# pull in shared compiler settings
+include ../common.mk
+
+# per-example flags
+# CXXFLAGS += -pthread
+
+## get it from the folder name
+TARGET := $(notdir $(CURDIR))
+SRCS   := $(wildcard *.cpp)
+OBJS   := $(SRCS:.cpp=.o)
+
+all: $(TARGET)
+
+$(TARGET): $(OBJS)
+	$(CXX) $(CXXFLAGS) -o $@ $^
+
+%.o: %.cpp
+	$(CXX) $(CXXFLAGS) -c $< -o $@
+
+run: $(TARGET)
+	./$(TARGET) $(ARGS)
+
+clean:
+	rm -f $(OBJS) $(TARGET)
+
+# Delegates to top-level Makefile
+check-format:
+	$(MAKE) -f ../Makefile check-format DIR=$(CURDIR)
+
+.PHONY: all clean run check-format

pi/main.cpp

@@ -0,0 +1,27 @@
+#include <iostream>
+#include <cstdlib>
+#include <iomanip>
+
+int
+main(int argc, char* argv[])
+{
+    long long iterations = 1000000;
+    if (argc > 1) {
+        iterations = std::atoll(argv[1]);
+    }
+
+    double sum = 0.0;
+
+    for (long long i = 0; i < iterations; ++i) {
+        double term = 1.0 / (2.0 * i + 1.0);
+        if (i % 2 == 0)
+            sum += term;
+        else
+            sum -= term;
+    }
+
+    double pi = 4.0 * sum;
+
+    std::cout << std::setprecision(15);
+    std::cout << pi << "\n";
+}

pi/tests.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+set -ex
+
+# Run the tests
+pi=$(./pi)
+
+# Check that the result is within a reasonable range
+if (( $(echo "$pi < 3.0" | bc -l) )) ||
+   (( $(echo "$pi > 3.2" | bc -l) )); then
+    echo "Test failed: pi is out of range: $pi"
+    exit 1
+else
+    echo "Test passed: pi is within range: $pi"
+fi