Search Results for author: Amir Ali Ahmadi

Found 13 papers, 1 papers with code

Higher-Order Newton Methods with Polynomial Work per Iteration

no code implementations10 Nov 2023 Amir Ali Ahmadi, Abraar Chaudhry, Jeffrey Zhang

At each step, our $d^{\text{th}}$-order method uses semidefinite programming to construct and minimize a sum of squares-convex approximation to the $d^{\text{th}}$-order Taylor expansion of the function we wish to minimize.

Safely Learning Dynamical Systems

no code implementations20 May 2023 Amir Ali Ahmadi, Abraar Chaudhry, Vikas Sindhwani, Stephen Tu

For $T=2$, we give a semidefinite representation of the set of safe initial conditions and show that $\lceil n/2 \rceil$ trajectories generically suffice for safe learning.

Sums of Separable and Quadratic Polynomials

no code implementations11 May 2021 Amir Ali Ahmadi, Cemil Dibek, Georgina Hall

We establish that the answer to question (i) is positive for univariate plus quadratic polynomials and for convex SPQ polynomials, but negative already for bivariate quartic SPQ polynomials.

Safely Learning Dynamical Systems from Short Trajectories

no code implementations24 Nov 2020 Amir Ali Ahmadi, Abraar Chaudhry, Vikas Sindhwani, Stephen Tu

For our first two results, we consider the setting of safely learning linear dynamics.

Learning Dynamical Systems with Side Information

1 code implementation L4DC 2020 Amir Ali Ahmadi, Bachir El Khadir

We then demonstrate the added value of side information for learning the dynamics of basic models in physics and cell biology, as well as for learning and controlling the dynamics of a model in epidemiology.

Epidemiology

Complexity aspects of local minima and related notions

no code implementations14 Aug 2020 Amir Ali Ahmadi, Jeffrey Zhang

We consider the notions of (i) critical points, (ii) second-order points, (iii) local minima, and (iv) strict local minima for multivariate polynomials.

On the complexity of finding a local minimizer of a quadratic function over a polytope

no code implementations12 Aug 2020 Amir Ali Ahmadi, Jeffrey Zhang

We show that unless P=NP, there cannot be a polynomial-time algorithm that finds a point within Euclidean distance $c^n$ (for any constant $c \ge 0$) of a local minimizer of an $n$-variate quadratic function over a polytope.

A Survey of Recent Scalability Improvements for Semidefinite Programming with Applications in Machine Learning, Control, and Robotics

no code implementations14 Aug 2019 Anirudha Majumdar, Georgina Hall, Amir Ali Ahmadi

Historically, scalability has been a major challenge to the successful application of semidefinite programming in fields such as machine learning, control, and robotics.

BIG-bench Machine Learning

On the Complexity of Detecting Convexity over a Box

no code implementations16 Jun 2018 Amir Ali Ahmadi, Georgina Hall

As a byproduct, our proof shows that the problem of testing whether all matrices in an interval family are positive semidefinite is strongly NP-hard.

Open-Ended Question Answering

Response to "Counterexample to global convergence of DSOS and SDSOS hierarchies"

no code implementations9 Oct 2017 Amir Ali Ahmadi, Anirudha Majumdar

In a recent note [8], the author provides a counterexample to the global convergence of what his work refers to as "the DSOS and SDSOS hierarchies" for polynomial optimization problems (POPs) and purports that this refutes claims in our extended abstract [4] and slides in [3].

DSOS and SDSOS Optimization: More Tractable Alternatives to Sum of Squares and Semidefinite Optimization

no code implementations8 Jun 2017 Amir Ali Ahmadi, Anirudha Majumdar

The reliance of this technique on large-scale semidefinite programs however, has limited the scale of problems to which it can be applied.

valid

Geometry of 3D Environments and Sum of Squares Polynomials

no code implementations22 Nov 2016 Amir Ali Ahmadi, Georgina Hall, Ameesh Makadia, Vikas Sindhwani

Motivated by applications in robotics and computer vision, we study problems related to spatial reasoning of a 3D environment using sublevel sets of polynomials.

DC Decomposition of Nonconvex Polynomials with Algebraic Techniques

no code implementations6 Oct 2015 Amir Ali Ahmadi, Georgina Hall

We consider the problem of decomposing a multivariate polynomial as the difference of two convex polynomials.

valid

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