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Illustration of gradient descent on a series of level sets. Gradient descent is based on the observation that if the multi-variable function is defined and differentiable in a neighborhood of a point , then () decreases fastest if one goes from in the direction of the negative gradient of at , ().
where y and f may denote vectors (in which case this equation represents a system of coupled ODEs in several variables). We are given the function f(t,y) and the initial conditions (a, y a), and we are interested in finding the solution at t = b. Let y(b) denote the exact solution at b, and let y b denote the solution that we compute.
The name arises for two reasons. First, the method relies on computing the solution in small steps, and treating the linear and the nonlinear steps separately (see below). Second, it is necessary to Fourier transform back and forth because the linear step is made in the frequency domain while the nonlinear step is made in the time domain.
The Heaviside step function, or the unit step function, usually denoted by H or θ (but sometimes u, 1 or 𝟙), is a step function named after Oliver Heaviside, the value of which is zero for negative arguments and one for positive arguments. Different conventions concerning the value H(0) are in use.
The deceleration parameter in cosmology is a dimensionless measure of the cosmic acceleration of the expansion of space in a Friedmann–Lemaître–Robertson–Walker universe. It is defined by: q = d e f − a ¨ a a ˙ 2 {\displaystyle q\ {\stackrel {\mathrm {def} }{=}}\ -{\frac {{\ddot {a}}a}{{\dot {a}}^{2}}}} where a {\displaystyle a} is ...
In mathematics, Anderson acceleration, also called Anderson mixing, is a method for the acceleration of the convergence rate of fixed-point iterations.Introduced by Donald G. Anderson, [1] this technique can be used to find the solution to fixed point equations () = often arising in the field of computational science.
Code Year was a free incentive Codecademy program intended to help people follow through on a New Year's Resolution to learn how to program, by introducing a new course for every week in 2012. [32] Over 450,000 people took courses in 2012, [33] [34] and Codecademy continued the program into 2013. Even though the course is still available, the ...
In the ADM formulation of general relativity, spacetime is split into spatial slices and a time axis.The basic variables are taken to be the induced metric on the spatial slice and the metric's conjugate momentum (), which is related to the extrinsic curvature and is a measure of how the induced metric evolves in time. [1]