Computes the eigenvalues of a symmetric tridiagonal matrix by bisection.
routinecomputes the eigenvalues of a symmetric tridiagonal matrix in parallel. These may be all eigenvalues, all eigenvalues in the interval
[, or the eigenvalues
iu. A static partitioning of work is done at the beginning of
p?stebzwhich results in all processes finding an (almost) equal number of eigenvalues.
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Notice revision #20110804
This notice covers the following instruction sets: SSE2, SSE4.2, AVX2, AVX-512.
- (global)TheINTEGER.BLACScontext handle.
- (global)Must beCHARACTER.'A'or'V'or'I'.If, therange='A'routinecomputes all eigenvalues.If, therange='V'routinecomputes eigenvalues in the interval[.vl,vu]If, therange='I'routinecomputes eigenvalueswith indicesilthroughiu.
- (global)Must beCHARACTER.'B'or'E'.If, the eigenvalues are to be ordered from smallest to largest within each split-off block.order='B'If, the eigenvalues for the entire matrix are to be ordered from smallest to largest.order='E'
- (global)The order of the tridiagonal matrixINTEGER.T(.n≥0)
- (global)REALforpsstebzDOUBLE PRECISIONforpdstebz.If, therange='V'routinecomputes the lower and the upper bounds for the eigenvalues on the interval[.1,vu]Iforrange='A''I',vlandvuare not referenced.
- (global)Constraint:INTEGER.1≤.il≤iu≤nIf, the index of therange='I'