LEADER 
01687cam a22001931574500 
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22ch1199801313 
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cr  
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981030s1998 xx eng 
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a eng

037 


n urn:nbn:de:bsz:ch1199801313

100 


a Benhammouda, B.

245 


a Rankrevealing topdown ULV factorizations

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b Universitätsbibliothek Chemnitz
c 1998
9 (issued 19981030)

520 
3 

a Rankrevealing ULV and URV factorizations are useful tools to determine the rank and to compute bases for nullspaces of a matrix. However, in the practical ULV (resp. URV ) factorization each left (resp. right) null vector is recomputed from its corresponding right (resp. left) null vector via triangular solves. Triangular solves are required at initial factorization, refinement and updating. As a result, algorithms based on these factorizations may be expensive, especially on parallel computers where triangular solves are expensive. In this paper we propose an alternative approach. Our new rankrevealing ULV factorization, which we call ¨topdown¨ ULV factorization ( TDULV factorization) is based on right null vectors of lower triangular matrices and therefore no triangular solves are required. Right null vectors are easy to estimate accurately using condition estimators such as incremental condition estimator (ICE). The TDULV factorization is shown to be equivalent to the URV factorization with the advantage of circumventing triangular solves.

500 


a preprint

856 
4 
1 
u https://nbnresolving.org/urn:nbn:de:bsz:ch1199801313
z OnlineZugriff

650 

4 
a MSC 65F15

082 
0 

a 510

980 


a urn:nbn:de:bsz:ch1199801313
b 22
c sid22colqucosa
