Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Enhanced parallelization of the incremental 4D-Var data assimilation
  algorithm using the Randomized Incremental Optimal Technique (RIOT)   Incremental 4D-Var is a data assimilation algorithm used routinely at
operational numerical weather predictions centers worldwide.This paper
implements a new method for parallelizing incremental 4D-Var, the Randomized
Incremental Optimal Technique (RIOT), which replaces the traditional sequential
conjugate gradient (CG) iterations in the inner-loop of the minimization with
fully parallel randomized singular value decomposition (RSVD) of the
preconditioned Hessian of the cost function. RIOT is tested using the standard
Lorenz-96 model (L-96) as well as two realistic high-dimensional atmospheric
source inversion problems based on aircraft observations of black carbon
concentrations. A new outer-loop preconditioning technique tailored to RSVD was
introduced to improve convergence stability and performance. Results obtained
with the L-96 system show that the performance improvement from RIOT compared
to standard CG algorithms increases significantly with non-linearities.
Overall, in the realistic black carbon source inversion experiments, RIOT
reduces the wall-time of the 4D-Var minimization by a factor 2-3, at the cost
of a factor 4-10 increase in energy cost due to the large number of parallel
cores used. Furthermore, RIOT enables reduction of the wall-time computation of
the analysis error covariance matrix by a factor 40 compared to a standard
iterative Lanczos approach. Finally, as evidenced in this study, implementation
of RIOT in an operational numerical weather prediction system will require a
better understanding of its convergence properties as a function of the Hessian
characteristics and, in particular, the degree of freedom for signal (DOFs) of
the inverse problem.

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The categories of this paper are: cond-mat
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-th
35
The categories of this paper are: mtrl-th
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The categories of this paper are: adap-org
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-bio
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The categories of this paper are: solv-int
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The categories of this paper are: hep-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: eess
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The categories of this paper are: comp-gas
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The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph