elpa_generalized_eigenvectors \- computes the generalized eigenvalues and (part of) the eigenvector spectrum for a real symmetric or complex hermitian matrix
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.SH SYNOPSIS
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.SS FORTRAN INTERFACE
use elpa
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class(elpa_t), pointer :: elpa
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.RI "call elpa%\fBgeneralized_eigenvectors\fP (a, b, ev, q, sc_desc, is_already_decomopsed, error)"
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.RI " "
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.RI "With the definitions of the input and output variables:"
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.RI "class(elpa_t) :: \fBelpa\fP ! returns an instance of the ELPA object"
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.TP
.RI "datatype :: \fBa\fP"
The matrix a for which the eigenvalues should be computed. The dimensions of matrix a must be set \fIBEFORE\fP with the methods \fBelpa_set\fP(3) and \fBelpa_setup\fP(3). The datatype of the matrix can be one of "real(kind=c_double)", "real(kind=c_float)", "complex(kind=c_double)", or "complex(kind=c_float)"
.TP
.RI "datatype :: \fBb\fP"
The matrix b defining the generalized eigenvalue problem. The dimensions and datatype fo the matrix has to be the same as for matrix a.
.TP
.RI "datatype :: \fBev\fP"
The vector ev where the eigenvalues will be stored in \fIascending\fP order. The datatype of the vector ev can be either "real(kind=c_double)", or "real(kind=c_float)", depending of the datatype of the matrix. Note that complex hermitian matrices also have real valued eigenvalues.
.RI "datatype :: \fBq\fP"
The storage space for the computed eigenvectors. The dimensions of matrix a must be set \fIBEFORE\fP with the methods \fBelpa_set\fP(3) and \fBelpa_setup\fP(3). The datatype of the matrix can be one of "real(kind=c_double)", "real(kind=c_float)", "complex(kind=c_double)", or "complex(kind=c_float)"
.TP
.RI "integer, optional :: \fBerror\fP"
The return error code of the function. Should be "ELPA_OK". The error code can be querried with the function \fBelpa_strerr\fP(3)
.RI "With the definitions of the input and output variables:"
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.TP
.RI "elpa_t \fBhandle\fP;"
The handle to the ELPA object
.TP
.RI "datatype *\fBa\fP;"
The matrix a for which the eigenvalues should be computed. The dimensions of the matrix must be set \fIBEFORE\fP with the methods \fBelpa_set\fP(3) and \fBelpa_setup\fP(3). The \fBdatatype\fP can be one of "double", "float", "double complex", or "float complex".
.TP
.RI "datatype *\fBev\fP;"
The storage for the computed eigenvalues. Eigenvalues will be stored in \fIascendig\fP order. The \fBdatatype\fP can be either "double" or "float". Note that the eigenvalues of complex hermitian matrices are also real.
.TP
.RI "datatype *\fBq\fP;"
The storage space for the computed eigenvectors. The dimensions of the matrix must be set \fIBEFORE\fP with the methods \fBelpa_set\fP(3) and \fBelpa_setup\fP(3). The \fBdatatype\fP can be one of "double", "float", "double complex", or "float complex".
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.RI "int *\fBerror\fP;"
The error code of the function. Should be "ELPA_OK". The error codes can be querried with \fBelpa_strerr\fP(3)
.SH DESCRIPTION
Compute the eigenvalues and (parts of) the eigenvector spectrum of a real symmtric or complex hermitian matrix.The functions \fBelpa_init\fP(3), \fBelpa_allocate\fP(3), \fBelpa_set\fP(3), and \fBelpa_setup\fP(3) must be called \fIBEFORE\fP \fBelpa_eigenvalues\fP can be called. Especially the number of eigenvectors to be computed can be set with \fPelpa_set\fB(3)