### Summary

Stochastic Optimization represents a suite of methods that make use of random processes to solve optimization problems, which are omnipresent in AI and data science. It helps to optimize results when perfect information isn’t available, turning uncertainty to our advantage.

### ELI5

Imagine playing the kids’ game of “hot and cold” but in a room where, randomly, echoes can mislead you about the direction. Stochastic Optimization is a way of playing this game, expecting these misleading signals, but still steadily moving toward the prize.

### In-depth explanation

Stochastic Optimization refers to a gamut of techniques that are used to find approximate solutions to complex optimization problems using aspects of randomness. These problems are often too convoluted or large to solve exactly, thus necessitating the usage of methods that deliver good-enough solutions.

A crucial use-case of these methods is when dealing with noisiness in the data. In real-world scenarios, observations are usually tainted with noise or incomplete. Deterministic optimization approaches can falter in these settings, potentially leading to brittle and volatile models that overfit the training noise. Stochastic optimization methods, on the other hand, conceptualise this situation and work upon average performance across many problem instances, aiding in finding more robust solutions.

One such well-known method is Stochastic Gradient Descent (SGD). Unlike gradient descent, which calculates the true gradient using the entire dataset, SGD approximates the gradient using a subset, or a single random instance, leading to a much faster but noisier convergence. The randomness in SGD helps to avoid local minima on non-convex error surfaces, providing a potential avenue towards the global minimum.

Another category is Stochastic Approximation, where function evaluations contain noise, and optimizing requires dealing with these noisy estimates. For example, the Robbins-Monro algorithm, a classic stochastic approximation method, is a recursive method for tuning parameters iteratively using noisy data.

Simulated Annealing is another heuristic stochastic optimization approach loosely based on the annealing process in metallurgy. This is a process where a metal’s temperature is slowly lowered to minimize defects, similar to moving towards an optimum in the problem space.

When the objective function is expensive to evaluate, methods like Bayesian Optimization, Evolutionary Algorithms, Particle Swarm Optimization, etc., that are based on surrogate modelling and intelligent sampling, become particularly useful.

To sum up, Stochastic Optimization provides an assortment of strategies that smartly use randomness and approximations to find solutions to intricate optimization problems that are often riddled with noise, high dimensionality, non-convexities, and other computational challenges.

### Related terms

Stochastic Gradient Descent, Simulated Annealing, Robbins-Monro Algorithm, Bayesian Optimization, Evolutionary Algorithms, Particle Swarm Optimization, Optimization, Overfitting, Gradient Descent, Convexity.