Results 1  10
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893
LSQR: An Algorithm for Sparse Linear Equations and Sparse Least Squares
 ACM Trans. Math. Software
, 1982
"... An iterative method is given for solving Ax ~ffi b and minU Ax b 112, where the matrix A is large and sparse. The method is based on the bidiagonalization procedure of Golub and Kahan. It is analytically equivalent to the standard method of conjugate gradients, but possesses more favorable numerica ..."
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Cited by 649 (21 self)
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An iterative method is given for solving Ax ~ffi b and minU Ax b 112, where the matrix A is large and sparse. The method is based on the bidiagonalization procedure of Golub and Kahan. It is analytically equivalent to the standard method of conjugate gradients, but possesses more favorable numerical properties. Reliable stopping criteria are derived, along with estimates of standard errors for x and the condition number of A. These are used in the FORTRAN implementation of the method, subroutine LSQR. Numerical tests are described comparing I~QR with several other conjugategradient algorithms, indicating that I~QR is the most reliable algorithm when A is illconditioned. Categories and Subject Descriptors: G.1.2 [Numerical Analysis]: ApprorJmationleast squares approximation; G.1.3 [Numerical Analysis]: Numerical Linear Algebralinear systems (direct and
Obliq  A language with distributed scope
, 1995
"... computation. An Obliq computation may involve multiple threads of control within an address space, multiple address spaces on a machine, heterogeneous machines over a local network, and multiple networks over the Internet. Obliq objects have state and are local to a site. Obliq computations can roam ..."
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Cited by 433 (12 self)
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computation. An Obliq computation may involve multiple threads of control within an address space, multiple address spaces on a machine, heterogeneous machines over a local network, and multiple networks over the Internet. Obliq objects have state and are local to a site. Obliq computations can roam over the network, while maintaining network connections.
2004): On the empirics of foreign aid and growth
 Economic Journal
"... The present paper reexamines the effectiveness of foreign aid theoretically and empirically. Using a standard OLG model we show that aid inflows will in general affect longrun productivity. The size and direction of the impact may depend on policies, ‘deep ’ structural characteristics and the siz ..."
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Cited by 131 (8 self)
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The present paper reexamines the effectiveness of foreign aid theoretically and empirically. Using a standard OLG model we show that aid inflows will in general affect longrun productivity. The size and direction of the impact may depend on policies, ‘deep ’ structural characteristics and the size of the inflow. The empirical analysis investigates these possibilities. Overall we find that aid has been effective in spurring growth, but the magnitude of the effect depends on climaterelated circumstances. Finally, we argue that the CollierDollar allocation rule should be seriously reconsidered by donor agencies if aid effectiveness is related to climate. The usefulness of foreign aid in promoting growth in developing countries has been an area of controversy ever since RosensteinRodan in 1943 advocated for aid to Eastern and SouthEastern Europe. Browsing through successive editions of a leading textbook in development economics provides a telling illustration of how the confidence in aid effectiveness dwindled over the years. In the first edition of ‘Leading Issues in Economic Development’, Meier (1964) dedicated a full 18page section to the issue of foreign aid. He started out asking: ‘How much aid?’. By the
Fast polar decomposition of an arbitrary matrix
 SIAM J. Sci. Stat. Comput
, 1990
"... Abstract. The polar decomposition of an m x n matrix A of full rank, where rn n, can be computed usingaquadraticallyconvergentalgorithmofHigham SIAMJ. Sci. Statist. Comput.,7 (1986), pp. 11601174]. The algorithm is based on a Newton iteration involving a matrix inverse. It is shown how, with the us ..."
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Cited by 40 (9 self)
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inversion based iteration to a matrix multiplication based iteration due to Kovarik, and to Bj6rck and Bowie, is formulated. The decision when to switch is made using a condition estimator. This "matrix multiplication rich " algorithm is shown to be more efficient on machines for which
An Introduction to Bioinformatics Algorithms
, 2004
"... In the early 1990s when one of us was teaching his first bioinformatics class, he was not sure that there would be enough students to teach. Although ..."
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Cited by 83 (1 self)
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In the early 1990s when one of us was teaching his first bioinformatics class, he was not sure that there would be enough students to teach. Although
Supersymmetry breaking from a CalabiYau singularity
, 2005
"... We conjecture a geometric criterion for determining whether supersymmetry is spontaneously broken in certain string backgrounds. These backgrounds contain wrapped branes at CalabiYau singularites with obstructions to deformation of the complex structure. We motivate our conjecture with a particular ..."
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Cited by 70 (4 self)
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We conjecture a geometric criterion for determining whether supersymmetry is spontaneously broken in certain string backgrounds. These backgrounds contain wrapped branes at CalabiYau singularites with obstructions to deformation of the complex structure. We motivate our conjecture with a particular example: the Y 2,1 quiver gauge theory corresponding to a cone over the first del Pezzo surface, dP1. This setup can be analyzed using ordinary supersymmetric field theory methods, where we find that gaugino condensation drives a deformation of the chiral ring which has no solutions. We expect this breaking to be a general feature of any theory of branes at a singularity with a smaller number of possible deformations than independent anomalyfree fractional branes.
Fundamentals of implementing RealTime Control Applications in Distributed Computer Systems
 J. of RealTime Systems
, 1998
"... Automatic control applications are realtime systems which pose stringent requirements on precisely timetriggered synchronized actions and constant endtoend delays in feedback loops which involve multirate interactions. Motivated by the apparent gap between computer science and automatic control ..."
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Cited by 69 (2 self)
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Automatic control applications are realtime systems which pose stringent requirements on precisely timetriggered synchronized actions and constant endtoend delays in feedback loops which involve multirate interactions. Motivated by the apparent gap between computer science and automatic control theory, a set of requirements for realtime implementation of control applications is given. A realtime behavioral model for control applications is then presented and exemplified. Important sources and characteristics of timevariations in distributed computer systems are investigated. This illuminates key execution strategies to ensure the required timing behaviour. Implications on design and implementation and directions for further work are discussed.
the Potchefstroom Campus of the NorthWest University Academic Supervisor: Mr. B.J. Linde
, 2004
"... Ihc articlc mlkcs two contibuttons to thc ps!rhologcal contract l~tcraturc: tt csamrncs the cclc\ancc of thc ps~chok~gical contract in a South. \ f~ican mimng enrimnmcnt; and it prondcs d d c d \;tluc o n tlrc psychological contract htcraturc oC penn:mcnr;md temporan persont~cl. 1:rwn thc htcr;tru ..."
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Ihc articlc mlkcs two contibuttons to thc ps!rhologcal contract l~tcraturc: tt csamrncs the cclc\ancc of thc ps~chok~gical contract in a South. \ f~ican mimng enrimnmcnt; and it prondcs d d c d \;tluc o n tlrc psychological contract htcraturc oC penn:mcnr;md temporan persont~cl. 1:rwn thc htcr;trurc it seems that the nru. pqcholog~clcal contl;~t is morc tr:ins~ction:d;~nd rcplacrd rhr <,Id relattotul ps~chc~k~gic;d ontmcl. 'Ibercfolc, tlw use of t e t n p o r a ~ ~ personnel is more commrm m orgmfi~tionswitlt pperfo~mance detennirung pay. I t was foond that cach ps~cholog~c,d contctct Is uniqmr and if there is no clrar ct,r~unonicati<,~~, contr;lct l m d ~ or viola no^ ^ can occur..i rwult of the new psyhologcal contract is n trust pap that comcs ulto cxwcnce. Thclehe, orgmis;tta,ns k c a new challcqge of ovcrcomin ~ this and mamtaining loydt!. The c m p i r d ~nvcsngaiion slrowcd that pcrm,ment pcrsonncl cspe~iencc the p s j c h o l o g d contr;tct morr positwc th;tn thc tcnqwmm pc~xmncl. 7 1 ~ s can ire atmlrutcd to thc srrongcr icl;~ta,nsl~ip hcnvccn pcnnmcnr personnel;and the rq;tnls;tmwl.
A review on the inverse of symmetric tridiagonal and block tridiagonal matrices
 SIAM J. Matrix Anal. Appl
, 1992
"... Abstract. In this paper some results are reviewed concerning the characterization of inverses of symmetric tridiagonal and block tridiagonal matrices as well as results concerning the decay of the elements of the inverses. These results are obtained by relating the elements of inverses to elements o ..."
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Cited by 68 (1 self)
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Abstract. In this paper some results are reviewed concerning the characterization of inverses of symmetric tridiagonal and block tridiagonal matrices as well as results concerning the decay of the elements of the inverses. These results are obtained by relating the elements of inverses to elements of the Cholesky decompositions of these matrices. This gives explicit formulas for the elements of the inverse and gives rise to stable algorithms to compute them. These expressions also lead to bounds for the decay of the elements of the inverse for problems arising from discretization schemes. Key words, block tridiagonal matrices, decay of elements AMS(MOS) subject classifications. 15A09, 65F50 1. Introduction. When
Results 1  10
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893