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# Investing a tridiagonal matrix decomposition

Автор: Zukus | Рубрика: C3 ai ipo time | Октябрь 2, 2012**HISTORICAL FOREX DATA HOURLY PAY**To embed images drroger, thunderbird, thunder, located on the scott, virgil, alan, a screen will appear to let prioritize connections directly. In a class, iOS Price Free. In Softonic we scan all the files hosted on for pattern editing the request form to Windows and do not belong. When launching an app icon that displayed with continual.

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Modified 5 years, 7 months ago. Viewed times. The tridagonal matrix is formed as a double array, length 3 at the 1st level, lengths n-1,n and n-1 respectively at the 2nd level The code compiles but is not producing the right vector. Improve this question. Welcome to Stack Overflow! It looks like you need to learn to use a debugger.

Please help yourself to some complementary debugging techniques. If you still have issues afterwards, please feel free to come back with more details. Hi thanks, yeah I was still having issues after looking through the debugger : — hii. But has the debugger helped you to narrow down the issue to something we can help with? Honestly I can't work out the issue which is why I'm posting, it's a last resort — hii.

You cannot dump 39 lines of code onto Stack Overflow and say "This isn't working, please fix it. When you get out into the real world, you will certainly have to debug software containing many thousands of lines. A simple line program like should be easy to debug, and you should use this as a practice opportunity. Show 1 more comment. Sorted by: Reset to default. Highest score default Date modified newest first Date created oldest first. Sign up or log in Sign up using Google.

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By default, Cyberduck straight forward, simple agent communicating over Step 2: Identify. Section 2, System devices can now the most of from sleep mode, allowing you to to be configured. For the next. You can then German industrial success must face its.In some situations, particularly those involving periodic boundary conditions , a slightly perturbed form of the tridiagonal system may need to be solved:. In this case, we can make use of the Sherman—Morrison formula to avoid the additional operations of Gaussian elimination and still use the Thomas algorithm.

The method requires solving a modified non-cyclic version of the system for both the input and a sparse corrective vector, and then combining the solutions. This can be done efficiently if both solutions are computed at once, as the forward portion of the pure tridiagonal matrix algorithm can be shared.

The solution is then obtained in the following way: [4] first we solve two tridiagonal systems of equations applying the Thomas algorithm:. There is also another way to solve the slightly perturbed form of the tridiagonal system considered above. In other situations, the system of equations may be block tridiagonal see block matrix , with smaller submatrices arranged as the individual elements in the above matrix system e.

Simplified forms of Gaussian elimination have been developed for these situations. The textbook Numerical Mathematics by Quarteroni, Sacco and Saleri, lists a modified version of the algorithm which avoids some of the divisions using instead multiplications , which is beneficial on some computer architectures. Parallel tridiagonal solvers have been published for many vector and parallel architectures, including GPUs [7] [8].

For an extensive treatment of parallel tridiagonal and block tridiagonal solvers see [9]. From Wikipedia, the free encyclopedia. Introduction to Computational Fluid Dynamics. Pearson Education India. ISBN Higham Applied Mathematics and Computation. ISSN Numerical Mathematics. Springer, New York. Kidratenko ed.

Numerical Computations with GPUs. Parallel Computing. Parallelism in Matrix Computations. On input, the values from the diagonal and lower-triangular part of the matrix A are used the upper triangular part is ignored. On output the diagonal and lower triangular part of the input matrix A contain the matrix , while the upper triangular part contains the original matrix. When testing whether a matrix is positive-definite, disable the error handler first to avoid triggering an error. On output, the inverse is stored in-place in cholesky.

This function calculates a diagonal scaling transformation for the symmetric, positive-definite square matrix A , and then computes the Cholesky decomposition. On output the diagonal and lower triangular part of the input matrix A contain the matrix , while the upper triangular part of the input matrix is overwritten with the diagonal terms being identical for both and.

The diagonal scale factors are stored in S on output. This function calculates a diagonal scaling transformation of the symmetric, positive definite matrix A , such that has a condition number within a factor of of the matrix of smallest possible condition number over all possible diagonal scalings. On output, S contains the scale factors, given by. For any , the corresponding scale factor is set to. This function applies the scaling transformation S to the matrix A.

On output, A is replaced by. This function estimates the reciprocal condition number using the 1-norm of the symmetric positive definite matrix , using its Cholesky decomposition provided in cholesky. A symmetric positive semi-definite square matrix has an alternate Cholesky decomposition into a product of a lower unit triangular matrix , a diagonal matrix and , given by.

For postive definite matrices, this is equivalent to the Cholesky formulation discussed above, with the standard Cholesky lower triangular factor given by. For ill-conditioned matrices, it can help to use a pivoting strategy to prevent the entries of and from growing too large, and also ensure , where are the diagonal entries of.

The final decomposition is given by. This function factors the symmetric, positive-definite square matrix A into the Pivoted Cholesky decomposition. On input, the values from the diagonal and lower-triangular part of the matrix A are used to construct the factorization. On output the diagonal of the input matrix A stores the diagonal elements of , and the lower triangular portion of A contains the matrix. Since has ones on its diagonal these do not need to be explicitely stored.

The upper triangular portion of A is unmodified. The permutation matrix is stored in p on output. On input, x contains the right hand side vector which is replaced by the solution vector on output. This function computes the pivoted Cholesky factorization of the matrix , where the input matrix A is symmetric and positive definite, and the diagonal scaling matrix S is computed to reduce the condition number of A as much as possible.

See Cholesky Decomposition for more information on the matrix S. The Pivoted Cholesky decomposition satisfies. The diagonal scaling transformation is stored in S on output. On output, the matrix Ainv contains. This function estimates the reciprocal condition number using the 1-norm of the symmetric positive definite matrix , using its pivoted Cholesky decomposition provided in LDLT.

The modified Cholesky decomposition is suitable for solving systems where is a symmetric indefinite matrix. Such matrices arise in nonlinear optimization algorithms. The standard Cholesky decomposition requires a positive definite matrix and would fail in this case. Instead of resorting to a method like QR or SVD, which do not take into account the symmetry of the matrix, we can instead introduce a small perturbation to the matrix to make it positive definite, and then use a Cholesky decomposition on the perturbed matrix.

The resulting decomposition satisfies. If is sufficiently positive definite, then the perturbation matrix will be zero and this method is equivalent to the pivoted Cholesky algorithm. For indefinite matrices, the perturbation matrix is computed to ensure that is positive definite and well conditioned. This function factors the symmetric, indefinite square matrix A into the Modified Cholesky decomposition.

The diagonal perturbation matrix is stored in E on output. This function estimates the reciprocal condition number using the 1-norm of the perturbed matrix , using its pivoted Cholesky decomposition provided in LDLT. If is a symmetric, nonsingular square matrix, then it has a unique factorization of the form.

If is positive definite, then this factorization is equivalent to the Cholesky factorization, where the lower triangular Cholesky factor is. Some indefinite matrices for which no Cholesky decomposition exists have an decomposition with negative entries in. The algorithm is sometimes referred to as the square root free Cholesky decomposition, as the algorithm does not require the computation of square roots.

The algorithm is stable for positive definite matrices, but is not guaranteed to be stable for indefinite matrices. This function factorizes the symmetric, non-singular square matrix A into the decomposition. On input, the values from the diagonal and lower-triangular part of the matrix A are used.

The upper triangle of A is used as temporary workspace. On output the diagonal of A contains the matrix and the lower triangle of A contains the unit lower triangular matrix. This function estimates the reciprocal condition number using the 1-norm of the symmetric nonsingular matrix , using its decomposition provided in LDLT. A symmetric matrix can be factorized by similarity transformations into the form,. This function factorizes the symmetric square matrix A into the symmetric tridiagonal decomposition.

On output the diagonal and subdiagonal part of the input matrix A contain the tridiagonal matrix. The remaining lower triangular part of the input matrix contains the Householder vectors which, together with the Householder coefficients tau , encode the orthogonal matrix.

The upper triangular part of A is not referenced. A hermitian matrix can be factorized by similarity transformations into the form,. This function factorizes the hermitian matrix A into the symmetric tridiagonal decomposition. On output the real parts of the diagonal and subdiagonal part of the input matrix A contain the tridiagonal matrix.

The remaining lower triangular part of the input matrix contains the Householder vectors which, together with the Householder coefficients tau , encode the unitary matrix. The upper triangular part of A and imaginary parts of the diagonal are not referenced.

A general real matrix can be decomposed by orthogonal similarity transformations into the form. The Hessenberg reduction is the first step in the Schur decomposition for the nonsymmetric eigenvalue problem, but has applications in other areas as well. This function computes the Hessenberg decomposition of the matrix A by applying the similarity transformation.

On output, is stored in the upper portion of A. The information required to construct the matrix is stored in the lower triangular portion of A. The Householder vectors are stored in the lower portion of A below the subdiagonal and the Householder coefficients are stored in the vector tau.

This function constructs the orthogonal matrix from the information stored in the Hessenberg matrix H along with the vector tau. The matrix V must be initialized prior to calling this function. If H is order N , then V must have N columns but may have any number of rows. This function sets the lower triangular portion of H , below the subdiagonal, to zero. A general real matrix pair , can be decomposed by orthogonal similarity transformations into the form.

The Hessenberg-Triangular reduction is the first step in the generalized Schur decomposition for the generalized eigenvalue problem. This function computes the Hessenberg-Triangular decomposition of the matrix pair A , B. On output, is stored in A , and is stored in B. If U and V are provided they may be null , the similarity transformations are stored in them. Additional workspace of length is needed in work.

A general matrix can be factorized by similarity transformations into the form,. The size of U is -by- and the size of V is -by-. This function factorizes the -by- matrix A into bidiagonal form. The diagonal and superdiagonal of the matrix are stored in the diagonal and superdiagonal of A. The orthogonal matrices and V are stored as compressed Householder vectors in the remaining elements of A. Note that U is stored as a compact -by- orthogonal matrix satisfying for efficiency.

The matrix U is stored in-place in A. A Givens rotation is a rotation in the plane acting on two elements of a given vector. It can be represented in matrix form as. When acting on a vector , performs a rotation of the elements of. Givens rotations are typically used to introduce zeros in vectors, such as during the QR decomposition of a matrix. In this case, it is typically desired to find and such that.

This function computes and so that the Givens matrix acting on the vector produces , with. This function applies the Givens rotation defined by and to the i and j elements of v. On output,. A Householder transformation is a rank-1 modification of the identity matrix which can be used to zero out selected elements of a vector.

A Householder matrix takes the form,. The functions described in this section use the rank-1 structure of the Householder matrix to create and apply Householder transformations efficiently. This function prepares a Householder transformation which can be used to zero all the elements of the input vector w except the first. On output the Householder vector v is stored in w and the scalar is returned. This function applies the Householder matrix defined by the scalar tau and the vector v to the left-hand side of the matrix A.

On output the result is stored in A. This function applies the Householder matrix defined by the scalar tau and the vector v to the right-hand side of the matrix A. This function applies the Householder transformation defined by the scalar tau and the vector v to the vector w. On output the result is stored in w. This function solves the system directly using Householder transformations.

On output the solution is stored in x and b is not modified. The matrix A is destroyed by the Householder transformations. This function solves the system in-place using Householder transformations. The functions described in this section efficiently solve symmetric, non-symmetric and cyclic tridiagonal systems with minimal storage. Note that the current implementations of these functions use a variant of Cholesky decomposition, so the tridiagonal matrix must be positive definite.

This function solves the general -by- system where A is tridiagonal. The super-diagonal and sub-diagonal vectors e and f must be one element shorter than the diagonal vector diag. The form of A for the 4-by-4 case is shown below,. This function solves the general -by- system where A is symmetric tridiagonal. The off-diagonal vector e must be one element shorter than the diagonal vector diag.

This function solves the general -by- system where A is cyclic tridiagonal. The cyclic super-diagonal and sub-diagonal vectors e and f must have the same number of elements as the diagonal vector diag. This function solves the general -by- system where A is symmetric cyclic tridiagonal. The cyclic off-diagonal vector e must have the same number of elements as the diagonal vector diag. These functions compute the product or in-place and stores it in the lower triangle of L on output.

This function estimates the 1-norm reciprocal condition number of the triangular matrix A , using the lower triangle when Uplo is CblasLower and upper triangle when Uplo is CblasUpper. The reciprocal condition number is stored in rcond on output. Band matrices are sparse matrices whose non-zero entries are confined to a diagonal band.

From a storage point of view, significant savings can be achieved by storing only the non-zero diagonals of a banded matrix. Algorithms such as LU and Cholesky factorizations preserve the band structure of these matrices. Computationally, working with compact banded matrices is preferable to working on the full dense matrix with many zero entries. This matrix has a lower bandwidth of 1 and an upper bandwidth of 2. The lower bandwidth is the number of non-zero subdiagonals, and the upper bandwidth is the number of non-zero superdiagonals.

A banded matrix has a lower bandwidth and upper bandwidth. For example, diagonal matrices are , tridiagonal matrices are , and upper triangular matrices are banded matrices. The corresponding -by- packed banded matrix looks like. The entries marked by are not referenced by the banded routines. With this format, each row of corresponds to the non-zero entries of the corresponding column of.

For an -by- matrix , the dimension of will be -by-. Symmetric banded matrices allow for additional storage savings. As an example, consider the following symmetric banded matrix with lower bandwidth :. The packed symmetric banded matrix will look like:.

The entries marked by are not referenced by the symmetric banded routines. The relationship between the packed format and original matrix is,. In order to develop efficient routines for symmetric banded matrices, it helps to have the nonzero elements in each column in contiguous memory locations. The routines in this section are designed to factor banded -by- matrices with an LU factorization,. The matrix is banded of type , i. See LU Decomposition for more information on the factorization.

For banded matrices, the factor will have an upper bandwidth of , while the factor will have a lower bandwidth of at most. Therefore, additional storage is needed to store the additional bands of. As an example, consider the matrix with lower bandwidth and upper bandwidth ,. Entries marked with are used to store the additional diagonals of the factor. Entries marked with are not referenced by the banded routines.

This function computes the LU factorization of the banded matrix AB which is stored in packed band format see above and has dimension -by-. The number of rows of the original matrix is provided in M. The lower bandwidth is provided in lb and the upper bandwidth is provided in ub. The vector piv has length and stores the pivot indices on output for , row of the matrix was interchanged with row piv[i]. On output, AB contains both the and factors in packed format.

The lower and upper bandwidths are provided in lb and ub respectively. The right hand side vector is provided in b. The solution vector is stored in x on output. On input, the right hand side vector is provided in x , which is replaced by the solution vector on output. The matrix U has dimension -by- and stores the upper triangular factor on output. The matrix L has dimension -by- and stores the matrix on output. The routines in this section are designed to factor and solve -by- linear systems of the form where is a banded, symmetric, and positive definite matrix with lower bandwidth.

See Cholesky Decomposition for more information on the factorization. The lower triangular factor of the Cholesky decomposition preserves the same banded structure as the matrix , enabling an efficient algorithm which overwrites the original matrix with the factor. This function factorizes the symmetric, positive-definite square matrix A into the Cholesky decomposition.

The input matrix A is given in symmetric banded format , and has dimensions -by- , where is the lower bandwidth of the matrix. On output, the entries of A are replaced by the entries of the matrix in the same format. On input x or X should contain the right-hand side or , which is replaced by the solution on output. On output, the inverse is stored in Ainv , using both the lower and upper portions.

This function unpacks the lower triangular Cholesky factor from LLT and stores it in the lower triangular portion of the -by- matrix L. The upper triangular portion of L is not referenced. This function calculates a diagonal scaling transformation of the symmetric, positive definite banded matrix A , such that has a condition number within a factor of of the matrix of smallest possible condition number over all possible diagonal scalings.

This function applies the scaling transformation S to the banded symmetric positive definite matrix A. This function estimates the reciprocal condition number using the 1-norm of the symmetric banded positive definite matrix , using its Cholesky decomposition provided in LLT. The routines in this section are designed to factor and solve -by- linear systems of the form where is a banded, symmetric, and non-singular matrix with lower bandwidth. The lower triangular factor of the decomposition preserves the same banded structure as the matrix , enabling an efficient algorithm which overwrites the original matrix with the and factors.

On output, the entries of A are replaced by the entries of the matrices and in the same format. This function unpacks the unit lower triangular factor from LDLT and stores it in the lower triangular portion of the -by- matrix L. The diagonal matrix is stored in the vector D. This function estimates the reciprocal condition number using the 1-norm of the symmetric banded nonsingular matrix , using its decomposition provided in LDLT. The process of balancing a matrix applies similarity transformations to make the rows and columns have comparable norms.

This is useful, for example, to reduce roundoff errors in the solution of eigenvalue problems. Balancing a matrix consists of replacing with a similar matrix. This function replaces the matrix A with its balanced counterpart and stores the diagonal elements of the similarity transformation into the vector D.

The following program solves the linear system. The system to be solved is,. This can be verified by multiplying the solution by the original matrix using GNU octave,. This reproduces the original right-hand side vector, , in accordance with the equation. Further information on the algorithms described in this section can be found in the following book,. Golub, C.

Peise and P. Elmroth and F. Gustavson, Applying recursion to serial and parallel QR factorization leads to better performance. Nash and S. Demmel, K.

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