Merge pull request #8 from DoctorLai/parallel-transform

Add C++ std::transform_reduce example

Author: doctorlai-msrc

README.md

@@ -15,13 +15,16 @@ Examples include (and will expand to):
 * [thread-safe-queue](./thread-safe-queue/)
 * Smart pointers
     * [unique-ptr-basics](./unique-ptr-basics/)
+    * [smart-ptr](./smart-ptr/)
 * Lock‑free / wait‑free data structures
 * Views
     * [views-zip-enumerate](./views-zip-enumerate/)
 * Atomics and memory ordering
 * Folding
     * [fold-left-fold-right](./fold-left-fold-right/)
 * RAII and ownership patterns
+* Parallelism
+    * [parallel-transform](./parallel-transform/)
 * Performance‑oriented C++ idioms
 
 ---

fold-left-fold-right/Makefile

@@ -4,7 +4,7 @@ include ../common.mk
 # per-example flags
 CXXFLAGS += -pthread
 
-TARGET := fold_left_fold_right
+TARGET := $(notdir $(CURDIR))
 SRCS   := main.cpp
 OBJS   := $(SRCS:.cpp=.o)
 

parallel-transform/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   := main.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

parallel-transform/main.cpp

@@ -0,0 +1,30 @@
+/**
+    This shows using parallel transform_reduce from C++17
+    to perform a fold (reduce) operation on a range of values. e.g. sum up 100 values in parallel
+*/
+#include <vector>
+#include <numeric>    // std::transform_reduce
+#include <functional> // std::plus
+#include <iostream>
+#include <execution> // std::execution::par
+
+int
+main()
+{
+    std::vector<int> numbers(100);
+    // Initialize the vector with values 1 to 100
+    std::iota(numbers.begin(), numbers.end(), 1);
+
+    // Use parallel transform_reduce to sum the values in parallel
+    int sum = std::transform_reduce(
+        std::execution::par, // parallel execution policy parallel or std::execution::seq for sequential
+        numbers.begin(),
+        numbers.end(),
+        0,                      // initial value
+        std::plus<int>{},       // binary operation to combine results
+        [](int v) { return v; } // unary operation to transform each element
+    );
+    std::cout << "Sum of numbers from 1 to 100: " << sum << '\n';
+
+    return 0;
+}

smart-ptr/Makefile

@@ -1,7 +1,7 @@
 CXX = g++
 CXXFLAGS = -std=c++23 -Wall -Wextra -g -I.
 
-TARGET = main
+TARGET := $(notdir $(CURDIR))
 SRCS = main.cpp
 
 all: $(TARGET)

thread-safe-queue/Makefile

@@ -4,7 +4,7 @@ include ../common.mk
 # per-example flags
 CXXFLAGS += -pthread
 
-TARGET := thread_safe_queue
+TARGET := $(notdir $(CURDIR))
 SRCS   := main.cpp
 OBJS   := $(SRCS:.cpp=.o)
 

unique-ptr-basics/Makefile

@@ -1,7 +1,7 @@
 # shared compiler configuration
 include ../common.mk
 
-TARGET := unique_ptr_basics
+TARGET := $(notdir $(CURDIR))
 SRCS   := main.cpp
 OBJS   := $(SRCS:.cpp=.o)
 

views-zip-enumerate/Makefile

@@ -4,7 +4,7 @@ include ../common.mk
 # per-example flags
 CXXFLAGS += -pthread
 
-TARGET := views-zip-enumerate
+TARGET := $(notdir $(CURDIR))
 SRCS   := main.cpp
 OBJS   := $(SRCS:.cpp=.o)