Add build benchmark script and results

Author: vinitkumar

BENCHMARK.md

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+# Chatbot Build Benchmark Results
+
+Benchmark comparing C and Zig implementations of the chatbot.
+
+**System:** macOS arm64  
+**Date:** 2026-01-12
+
+## Results
+
+| Metric | C | Zig | Difference |
+|--------|---|-----|-----------|
+| Build Time | 93ms | 710ms | Zig is 7.63x slower |
+| Executable Size | 33K | 1.3M | Zig is 39x larger |
+
+## Analysis
+
+### Build Time
+- **C (93ms)**: Fast compilation using GCC with minimal optimization
+- **Zig (710ms)**: Longer compilation time due to Zig's more comprehensive compiler
+
+The C version compiles significantly faster due to:
+- Simpler compilation pipeline
+- No build system overhead (direct gcc command)
+- Minimal type checking and analysis
+
+### Executable Size
+- **C (33K)**: Small, minimal runtime
+- **Zig (1.3M)**: Larger due to Zig's standard library and runtime
+
+The Zig executable is larger because:
+- Zig stdlib is embedded in the binary
+- More comprehensive runtime features
+- GeneralPurposeAllocator adds overhead
+
+## Notes
+
+- Both versions are unoptimized builds
+- C build uses `-std=c11 -Wall -Wextra -pedantic`
+- Zig build uses default optimization level
+- Times are from cold builds (no cache)
+
+## Running the Benchmark
+
+```bash
+./benchmark.sh
+```
+
+This will clean, rebuild both versions, and compare build times and sizes.

benchmark.sh

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+#!/bin/bash
+
+set -e
+
+echo "=========================================="
+echo "Chatbot Build Benchmark"
+echo "=========================================="
+echo ""
+
+# C Version Benchmark
+echo "C Version Benchmark"
+echo "------------------------------------------"
+
+cd c
+echo "Cleaning..."
+make clean > /dev/null 2>&1
+
+echo "Building C version..."
+C_START=$(date +%s%N)
+make > /dev/null 2>&1
+C_END=$(date +%s%N)
+C_TIME=$(( (C_END - C_START) / 1000000 ))  # Convert to milliseconds
+
+C_SIZE=$(ls -lh chat | awk '{print $5}')
+
+echo "Build time: ${C_TIME}ms"
+echo "Executable size: ${C_SIZE}"
+
+cd ..
+echo ""
+
+# Zig Version Benchmark
+echo "Zig Version Benchmark"
+echo "------------------------------------------"
+
+cd zig
+echo "Cleaning..."
+rm -rf zig-out .zig-cache > /dev/null 2>&1
+mkdir -p zig-out/bin
+
+echo "Building Zig version..."
+ZIG_START=$(date +%s%N)
+zig build-exe src/main.zig -femit-bin=zig-out/bin/chat > /dev/null 2>&1
+ZIG_END=$(date +%s%N)
+ZIG_TIME=$(( (ZIG_END - ZIG_START) / 1000000 ))  # Convert to milliseconds
+
+ZIG_SIZE=$(ls -lh zig-out/bin/chat | awk '{print $5}')
+
+echo "Build time: ${ZIG_TIME}ms"
+echo "Executable size: ${ZIG_SIZE}"
+
+cd ..
+echo ""
+
+# Comparison
+echo "Comparison"
+echo "------------------------------------------"
+if [ $C_TIME -lt $ZIG_TIME ]; then
+  RATIO=$(echo "scale=2; $ZIG_TIME / $C_TIME" | bc)
+  echo "C version is ${RATIO}x faster"
+else
+  RATIO=$(echo "scale=2; $C_TIME / $ZIG_TIME" | bc)
+  echo "Zig version is ${RATIO}x faster"
+fi
+
+echo ""
+echo "Summary:"
+echo "  C:   ${C_TIME}ms, ${C_SIZE}"
+echo "  Zig: ${ZIG_TIME}ms, ${ZIG_SIZE}"