layout: true class: typo, typo-selection --- count: false class: nord-dark, middle, center # Lecture 2a: Software Development Tips 💡 @luk036 👨‍💻 · 2026 📅 --- ## 🐉 Myths of Software Development - Computers are smart - C is fast; C++ is slow - I love programming --- ### 💬 Messages (I) - About 99% projects fail. - Software is "soft"; Hardware is "hard" - Automation is hard - Nightly build concept (Microsoft) - Agile software development - Pair programming - Extreme programming - Opensource projects - Continuous Integration --- ### 💬 Messages (II) - Forget about Matlab, embrace Python 🤔 - Forget about Perl, embrace Python 🤔 - Forget about C, embrace modern C++. - Modern C++ is faster, safer, and cleaner. ✨✨✨ - Forget about C++, embrace Python 🤔 - Strategy: Python first, C++ follows. - Forget about XML, embrace [JSON](https://json.org/). - Forget about HTML/LaTeX, embrace Markdown 🤔 - Strategy: Markdown first, LaTeX follows. - Forget about Verilog, embrace [MyHDL](http://www.myhdl.org/) --- ### Coding Tips 💡 - Test, test, test!!! - Write cleaner code - Refactor repeat codes - Object oriented programming - Generic programming - Design Pattern - Coroutine is your friend - Learn from good codes, not bad ones. - The last rescue: Google search. --- ### Software Development Best Practices 📋 .mermaid[ <pre> graph TD T("🧪 Test, Test, Test!!!") --> C("🧹 Clean Code") C --> R("♻️ Refactor") R --> D("🏗️ Design Patterns") D --> P("⚡ Performance Opt") T2("🔄 CI/CD") --> C P --> T2 style T fill:#c8e6c9,stroke:#2e7d32,stroke-width:3px style C fill:#e3f2fd,stroke:#1565c0,stroke-width:3px style R fill:#fff3e0,stroke:#e65100,stroke-width:3px style D fill:#f3e5f5,stroke:#7b1fa2,stroke-width:3px style P fill:#ffcdd2,stroke:#c62828,stroke-width:3px style T2 fill:#c8e6c9,stroke:#2e7d32,stroke-width:3px </pre> ] --- ### 🚀 Performance Tips 💡 - Avoid string comparison - Use sentinel - Use cheaper measure, avoid `sqrt()`, `sin()`, `cos()` - 🦥 Lazy evaluation - Table lookup - Avoid sequence search: - Backward pointers - Hash Table/Dictionary/Map --- ### 🚫 Avoid string comparison .pull-left[ Bad 👎: ```python if pin == "input": # ... elif pin == "output": # ... elif pin == "in_out": # ... elif pin == "dont_care": # ... else: # ... ``` ] .pull-right[ Better ⚡: ```python pin_type = dict({"input":0}, {"output":1}, {"in_out":2}, {"dont_care":3}) ... id = pin_type.get(pin, -1) if id == 0: # ... elif id == 1: # ... elif id == 2: # ... elif id == 3: # ... else: # ... ``` ] --- ### 🛡️ Use Sentinel .pull-left[ Bad 👎: .font-sm.mb-xs[ ```python max = 0 bckt = [Dllist() for _ in range(high)] # ... def popleft(): res = bckt[max].popleft() while max >= 0 and bckt[max].empty(): max -= 1 return res ``` ] ] .pull-right[ Better ⚡: .font-sm.mb-xs[ ```python max = 0 sentinel = Dllink() bckt = [Dllist() for _ in range(high+1)] bckt[0].append(sentinel) # sentinel # ... def popleft(): res = bckt[max].popleft() while bckt[max].empty(): max -= 1 return res # Saved a boundary check `max >= 0` ``` ] ] --- ### ⚡ Use cheaper measure .pull-left[ Bad 👎: ```python mind = 10000 maxd = 0 for u, v in G.edges(): t = vec[u] - vec[v] d = sqrt(t.dot(t)) if mind > d: mind = d if maxd < d: maxd = d return maxd - mind ``` ] .pull-right[ Better ⚡: ```python minq = 10000 maxq = 0 for u, v in G.edges(): t = vec[u] - vec[v] q = t.dot(t) if minq > q: minq = q if maxq < q: maxq = q return sqrt(maxq) - sqrt(minq) ``` ] --- ### 📚 Another Example .pull-left[ Bad 👎: ```python mind = 10000 maxd = 0 for u, v in G.edges(): t = 1 - vec[u].dot(vec[v]) d = arcsin(sqrt(t)) if mind > d: mind = d if maxd < d: maxd = d return maxd - mind ``` ] .pull-right[ Better ⚡: ```python minq = 10000 maxq = 0 for u, v in G.edges(): q = 1 - vec[u].dot(vec[v]) if minq > q: minq = q if maxq < q: maxq = q return arcsin(sqrt(maxq)) \ - arcsin(sqrt(minq)) ``` ] --- ### Optimization Tips 💡 - Convex optimization - Network optimization - Primal-dual --- count: false class: nord-dark, middle, center ## Q&A 🎤