Computing the Newton-step faster than Hessian accumulation
- URL: http://arxiv.org/abs/2108.01219v1
- Date: Mon, 2 Aug 2021 11:22:08 GMT
- Title: Computing the Newton-step faster than Hessian accumulation
- Authors: Akshay Srinivasan, Emanuel Todorov
- Abstract summary: We show that given the computational graph of the function, this bound can be reduced to $O(mtau3)$, where $tau, m$ are the width and size of a tree-decomposition of the graph.
The proposed algorithm generalizes nonlinear optimal-control methods based on LQR to general optimization problems and provides non-trivial gains in iteration-complexity even in cases where the Hessian is dense.
- Score: 8.147652597876862
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: Computing the Newton-step of a generic function with $N$ decision variables
takes $O(N^3)$ flops. In this paper, we show that given the computational graph
of the function, this bound can be reduced to $O(m\tau^3)$, where $\tau, m$ are
the width and size of a tree-decomposition of the graph. The proposed algorithm
generalizes nonlinear optimal-control methods based on LQR to general
optimization problems and provides non-trivial gains in iteration-complexity
even in cases where the Hessian is dense.
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