Comprehensive Introduction to AI: History, Models, and Optimization Techniques

Comprehensive Introduction to AI: History, Models, and Optimization Techniques

Introduction to AI and Course Overview

  • Welcome and introductions by instructors Percy and Dorsa, along with the teaching team specializing in NLP, machine learning, computer vision, and robotics.
  • Weekly sections cover review and advanced topics; first homework due next Tuesday via Gradescope.

Historical Context of AI

  • AI's origins trace back to the 1956 Dartmouth workshop led by John McCarthy, Marvin Minsky, and others aiming to simulate all aspects of intelligence.
  • Early optimism was tempered by computational limitations and the complexity of problems like machine translation, leading to the first AI winter.
  • The 1970s-80s saw a resurgence with expert systems encoding knowledge as rules, impacting industries but limited by manual effort and brittleness, causing a second AI winter.
  • Neural networks originated in 1943 with McCulloch and Pitts, but skepticism after the 1969 Perceptrons book slowed progress until the 1980s rediscovery of backpropagation.
  • Deep learning breakthroughs in 2012 (AlexNet) and successes like AlphaGo marked a transformative era.

Two Traditions in AI

  • Logical/symbolic AI (John McCarthy's tradition) vs. neuroscience-inspired AI (neural networks).
  • Despite philosophical differences, these traditions have synergies, exemplified by AlphaGo combining logic-based rules with neural network learning.
  • AI integrates diverse fields: statistics, economics, optimization, and computer science.

AI Goals: Agents vs. Tools

  • AI as agents: creating systems that mimic human intelligence, including perception, reasoning, and learning from few examples.
  • AI as tools: building systems to assist humans in practical tasks, such as poverty prediction from satellite imagery or energy optimization in data centers.
  • Challenges include adversarial examples, biases in models (e.g., gender bias in translation), and fairness issues in critical applications like criminal risk assessment.

Modeling, Inference, and Learning Paradigm

  • Modeling: Simplifying complex real-world problems into mathematically precise models (e.g., graphs for navigation).
  • Inference: Querying models to solve problems efficiently (e.g., shortest path).
  • Learning: Automatically fitting model parameters from data rather than manual encoding.
  • This paradigm underpins the course structure and final projects.

Course Topics Overview

  • Machine Learning: Emphasizes generalization from data, moving complexity from code to data.
  • Reflex Models: Fast, fixed computation models like linear classifiers and neural networks.
  • State-Based Models: Planning and decision-making models for games, robotics, and navigation, including search, stochastic, and adversarial settings.
  • Variable-Based Models: Constraint satisfaction problems and Bayesian networks for problems like Sudoku and tracking.
  • Logic and High-Level Intelligence: Systems capable of reasoning with heterogeneous information demonstrated via a logic-based interactive demo.

Course Logistics

  • Prerequisites: Programming, discrete math, probability.
  • Coursework: Eight homeworks (mix of written and programming), a project with milestones, and an exam focused on problem-solving.
  • Collaboration encouraged with strict honor code enforcement; no sharing of code or solutions publicly.
  • Communication via Piazza; late days policy and auto-grading details provided.

Technical Deep Dive: Optimization in AI

Dynamic Programming and Edit Distance

  • Problem: Compute minimum edits (insertions, deletions, substitutions) to transform one string into another.
  • Approach: Break down problem into subproblems using recursion and memoization to avoid exponential time complexity.
  • Implementation: Define recurrence relations, base cases, and use caching to optimize performance.

Continuous Optimization and Gradient Descent

  • Problem: Fit a regression line minimizing least squares error.
  • Concept: Abstract the objective function and use derivatives to guide optimization.
  • Algorithm: Gradient descent iteratively updates parameters by moving opposite to the gradient to find minimum error.
  • Demonstration: Python code example showing convergence of slope parameter to optimal value.

Summary

This lecture sets the foundation for understanding AI's evolution, core methodologies, and practical challenges. It introduces students to the modeling-inference-learning framework and essential optimization techniques that will be applied throughout the course. The session also emphasizes ethical considerations and the importance of rigorous problem-solving skills.

For those interested in diving deeper into AI concepts, consider exploring the following resources:

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