The design of a two-channel nonuniform-division filter (NDF) bank with infinite impulse response (IIR) analysis/synthesis filters and low group delay in the sense of L-1 error criteria is considered. The problem formu...
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The design of a two-channel nonuniform-division filter (NDF) bank with infinite impulse response (IIR) analysis/synthesis filters and low group delay in the sense of L-1 error criteria is considered. The problem formulation results in a nonlinear optimisation problem. Based on a variant of karmarkar's algorithm, the optimisation problem is solved through a frequency sampling and iterative approximation technique to find the tap coefficients and the reflection coefficients for the numerator and the denominator of the IIR analysis filters. An efficient stabilisation procedure ensures that the reflection coefficients lie in (-1, 1). Simulation results are provided for illustration and comparison.
karmarkar's algorithm for linear programming was published in 1984, and it is highly important to both theory and practice. On the practical side some of its variants have been found to be far more efficient than ...
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karmarkar's algorithm for linear programming was published in 1984, and it is highly important to both theory and practice. On the practical side some of its variants have been found to be far more efficient than the simplex method on a wide range of very large calculations, while its polynomial time properties are fundamental to research on complexity. These properties depend on the fact that each iteration reduces a ''potential function'' by an amount that is bounded away from zero, the bound being independent of all the coefficients that occur. It follows that, under mild conditions on the initial vector of variables, the number of iterations that are needed to achieve a prescribed accuracy in the final value of the linear objective function is at most a multiple of n, where n is the number of inequality constraints. By considering a simple example that allows n to be arbitrarily large, we deduce analytically that the magnitude of this complexity bound is correct. Specifically, we prove that the solution of the example by karmarkar's original algorithm can require about n/20 iterations. Further, we find that the algorithm makes changes to the variables that are closely related to the steps of the simplex method.
We give two results related to Gonzaga's recent paper showing that lower bounds derived from the Todd-Burrell update can be obtained by solving a one-variable linear programming problem involving the centering dir...
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We give two results related to Gonzaga's recent paper showing that lower bounds derived from the Todd-Burrell update can be obtained by solving a one-variable linear programming problem involving the centering direction and the affine direction. We show how these results may be used to update the primal solution when using the dual affine variant of karmarkar's algorithm. This leads to a dual projective algorithm.
In this paper, we study the global convergence of a large class of primal-dual interior point algorithms for solving the linearly constrained convex programming problem. The algorithms in this class decrease the value...
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In this paper, we study the global convergence of a large class of primal-dual interior point algorithms for solving the linearly constrained convex programming problem. The algorithms in this class decrease the value of a primal-dual potential function and hence belong to the class of so-called potential reduction algorithms. An inexact line search based on Armijo stepsize rule is used to compute the stepsize. The directions used by the algorithms are the same as the ones used in primal-dual path following and potential reduction algorithms and a very mild condition on the choice of the ''centering parameter'' is assumed. The algorithms always keep primal and dual feasibility and, in contrast to the polynomial potential reduction algorithms, they do not need to drive the value of the potential function towards - infinity in order to converge. One of the techniques used in the convergence analysis of these algorithms has its root in nonlinear unconstrained optimization theory.
Let phi be a convex homogeneous function of degree K>0 defined over the positive points of a subspace W of R(n), n greater-than-or-equal-to 2. Assume phi(x)>0 for some 00, there exists 0<x(d) is-an-element-of...
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Let phi be a convex homogeneous function of degree K>0 defined over the positive points of a subspace W of R(n), n greater-than-or-equal-to 2. Assume phi(x)>0 for some 00, there exists 0karmarkar's algorithm proves the above for the special case where phi is linear.
In a recent paper, Shaw and Goldfarb show that a version of the standard form projective algorithm can achieve O(square-root n L) step complexity, opposed to the O(nL) step complexity originally demonstrated for the a...
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In a recent paper, Shaw and Goldfarb show that a version of the standard form projective algorithm can achieve O(square-root n L) step complexity, opposed to the O(nL) step complexity originally demonstrated for the algorithm. The analysis of Shaw and Goldfarb shows that the algorithm, using a constant, fixed steplength, approximately follows the central trajectory. In this paper we show that simple modifications of the projective algorithm obtain the same complexity improvement, while permitting a linesearch of the potential function on each step. An essential component is the addition of a single constraint, motivated by Shaw and Goldfarb's analysis, which makes the standard form algorithm strictly monotone in the true objective.
We consider partial updating in Kojima, Mizuno, and Yoshise's primal-dual potential reduction algorithm for linear programming. We use a simple safeguard condition to control the number of updates incurred on comb...
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We consider partial updating in Kojima, Mizuno, and Yoshise's primal-dual potential reduction algorithm for linear programming. We use a simple safeguard condition to control the number of updates incurred on combined primal-dual steps. Our analysis allows for unequal steplengths in the primal and dual variables, which appears to be a computationally significant factor for primal-dual methods. The safeguard we use is a primal-dual Goldstein-Armijo condition, modified to deal with the unequal primal and dual steplengths.
We describe the convergence behavior of karmarkar's projective algorithm for solving a simple linear program. We show that the algorithm requires at least n - 1 iterations to reach the optimal solution, while the ...
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We describe the convergence behavior of karmarkar's projective algorithm for solving a simple linear program. We show that the algorithm requires at least n - 1 iterations to reach the optimal solution, while the simplex method may need one pivot step. Thus in the worst case, karmarkar's algorithm will require at least OMEGA(n) iterations to converge.
For a possibly degenerate linear program min x{c(T)x;Ax = b, x greater-than-or-equal-to 0} (A is an m X n real matrix, b is-an-element-of R(m) and c is-an-element-to R(n)), whose optimal value is 0, we study the limit...
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For a possibly degenerate linear program min x{c(T)x;Ax = b, x greater-than-or-equal-to 0} (A is an m X n real matrix, b is-an-element-of R(m) and c is-an-element-to R(n)), whose optimal value is 0, we study the limiting behavior of the trajectories of the family of vector fields [GRAPHICS] for all values of q greater-than-or-equal-to n, where X is the diagonal matrix associated with x and P(AX) is the projection operator onto the null space of AX. A polynomial algorithm based on the directions PHI(q)(x) has been presented by Gonzaga [6] when q = n or q = n + square-root n . We show that all trajectories of PHI(q)(x) converge to the unique "center" of the optimal face of the given linear program. When this face consists of a unique vertex, it is shown that any trajectory of PHI(q)(x) approaches this vertex along the same direction. When the optimal face consists of more than one point, we show that there is a threshold value tau > 0 such that: for q > tau, "most" of the trajectories of PHI(q)(x) converge to the "center" tangentially to the optimal face and that the direction of approach of a trajectory of PHI(q)(x) depends on the initial condition;for q < tau (q = tau), the trajectories of PHI(q)(x) converge to the "center" along a unique direction (along several directions which depend on the initial condition) forming a positive angle with the optimal face.
We consider partial updating in Ye's affine potential reduction algorithm for linear programming. We show that using a Goldstein-Armijo rule to safeguard a linesearch of the potential function during primal steps ...
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We consider partial updating in Ye's affine potential reduction algorithm for linear programming. We show that using a Goldstein-Armijo rule to safeguard a linesearch of the potential function during primal steps is sufficient to control the number of updates. We also generalize the dual step construction to apply with partial updating. The result is the first O(n3L) algorithm for linear programming whose steps are not constrained by the need to remain approximately centered. The fact that the algorithm has a rigorous "primal-only" initialization actually reduces the complexity to less than O(m1.5n1.5L).
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