From eigenvalues and initial representations computes the selected eigenvalues and eigenvectors of the real symmetric tridiagonal matrix in parallel on multiple processors.
?stegr2bshould only be called after a call to
?stegr2a. From eigenvalues and initial representations computed by
?stegr2bcomputes the selected eigenvalues and eigenvectors of the real symmetric tridiagonal matrix in parallel on multiple processors. It is potentially invoked multiple times on a given processor because the locally relevant representation tree might depend on spectral information that is "owned" by other processors and might need to be communicated.
- The calling sequence has two additional integer parameters,dolanddou, that should satisfym≥dou≥dol≥1. These parameters are only relevant for the casejobz= 'V'.?stegr2bonly computes the eigenvectors corresponding to eigenvaluesdolthroughdouinw. (That is, instead of computing the eigenvectors belonging to, only the eigenvectors belonging to eigenvaluesw(1) throughw(m)are computed. In this case, only the eigenvaluesw(dol) throughw(dou)are guaranteed to be accurately refined to all figures by Rayleigh-Quotient iteration.dol:dou
- The additional argumentsvstart,finish,ndepth,parity,zoffsetare included as a thread-safe implementation equivalent to save variables. These variables store details about the local representation tree which is computed layerwise. For scalability reasons, eigenvalues belonging to the locally relevant representation tree might be computed on other processors. These need to be communicated before the inspection of the RRRs can proceed on any given layer. Note that only when the variablefinishequals, the computation has ended. All eigenpairs between.TRUE.dolanddouhave been computed.mis set todou-dol+ 1.
Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.
Notice revision #20110804
This notice covers the following instruction sets: SSE2, SSE4.2, AVX2, AVX-512.
- CHARACTER*1= 'N': Compute eigenvalues only;= 'V': Compute eigenvalues and eigenvectors.