A Nearly Linear-Time PTAS for Explicit Fractional Packing and Covering   Linear Programs
  We give an approximation algorithm for packing and covering linear programs (linear programs with non-negative coefficients). Given a constraint matrix with n non-zeros, r rows, and c columns, the algorithm computes feasible primal and dual solutions whose costs are within a factor of 1+eps of the optimal cost in time O((r+c)log(n)/eps^2 + n). 
Christos Koufogiannakis and Neal E. Young