Reordering columns for smaller indexes

Reordering Columns for Smaller Indexes

Column-oriented indexes—such as projection or bitmap indexes—are compressed by run-length encoding to reduce storage and increase speed. Sorting the tables improves compression. On realistic data sets, permuting the columns in the right order before sorting can reduce the number of runs by a factor of two or more. For many cases, we prove that the number of runs in table columns is minimized if...

Smaller Self-indexes for Natural Language

Self-indexes for natural-language texts, where these are regarded as token (word or separator) sequences, achieve very attractive space and search time. However, they suffer from a space penalty due to their large vocabulary. In this paper we show that by replacing the Huffman encoding they implicitly use by the slightly weaker Hu-Tucker encoding, which respects the lexical order of the vocabul...

A Survey for the Selection of Control Structure for Distillation Columns Based on Steady State Controllability Indexes

Reordering Metrics for MT

One of the major challenges facing statistical machine translation is how to model differences in word order between languages. Although a great deal of research has focussed on this problem, progress is hampered by the lack of reliable metrics. Most current metrics are based on matching lexical items in the translation and the reference, and their ability to measure the quality of word order h...

a study on thermodynamic models for simulation of 1,3 butadiene purification columns

attempts have been made to study the thermodynamic behavior of 1,3 butadiene purification columns with the aim of retrofitting those columns to more energy efficient separation schemes. 1,3 butadiene is purified in two columns in series through being separated from methyl acetylene and 1,2 butadiene in the first and second column respectively. comparisons have been made among different therm...