A função não convexa is a mathematical function that does not exhibit the properties of convexity across its entire domain. In simpler terms, while a função convexa curves upward and has a single mínimo global, a non-convex function can have multiple peaks and valleys, leading to several local minima and maxima.
Matematicamente, uma função f(x) is considered non-convex if there exist points x1 and x2 within its domain such that the line segment connecting (x1, f(x1)) and (x2, f(x2)) lies below the function itself for some points between x1 and x2. This characteristic is significant in optimization problems, particularly in fields like aprendizado de máquina and pesquisa operacional, where the goal is often to find the minimum value of a function.
In optimization contexts, non-convex functions pose challenges because traditional algoritmos de otimização, such as gradient descent, may converge to local minima rather than the global minimum, making it difficult to find the best possible solution. This is particularly relevant in the training of complex machine learning models, where loss functions can be non-convex, leading to varying performance based on initial conditions and parameter settings.
Understanding the nature of non-convex functions is crucial for developing effective optimization strategies, including the use of techniques like simulated annealing, genetic algorithms, or advanced gradient-based methods designed to escape local minima.