The ELPA library: scalable parallel eigenvalue solutions for electronic structure theory and computational science.

Obtaining the eigenvalues and eigenvectors of large matrices is a key problem in electronic structure theory and many other areas of computational science. The computational effort formally scales as O(N(3)) with the size of the investigated problem, N (e.g. the electron count in electronic structure theory), and thus often defines the system size limit that practical calculations cannot overcome. In many cases, more than just a small fraction of the possible eigenvalue/eigenvector pairs is needed, so that iterative solution strategies that focus only on a few eigenvalues become ineffective. Likewise, it is not always desirable or practical to circumvent the eigenvalue solution entirely. We here review some current developments regarding dense eigenvalue solvers and then focus on the Eigenvalue soLvers for Petascale Applications (ELPA) library, which facilitates the efficient algebraic solution of symmetric and Hermitian eigenvalue problems for dense matrices that have real-valued and complex-valued matrix entries, respectively, on parallel computer platforms. ELPA addresses standard as well as generalized eigenvalue problems, relying on the well documented matrix layout of the Scalable Linear Algebra PACKage (ScaLAPACK) library but replacing all actual parallel solution steps with subroutines of its own. For these steps, ELPA significantly outperforms the corresponding ScaLAPACK routines and proprietary libraries that implement the ScaLAPACK interface (e.g. Intel's MKL). The most time-critical step is the reduction of the matrix to tridiagonal form and the corresponding backtransformation of the eigenvectors. ELPA offers both a one-step tridiagonalization (successive Householder transformations) and a two-step transformation that is more efficient especially towards larger matrices and larger numbers of CPU cores. ELPA is based on the MPI standard, with an early hybrid MPI-OpenMPI implementation available as well. Scalability beyond 10,000 CPU cores for problem sizes arising in the field of electronic structure theory is demonstrated for current high-performance computer architectures such as Cray or Intel/Infiniband. For a matrix of dimension 260,000, scalability up to 295,000 CPU cores has been shown on BlueGene/P.

Pelvic tilt in neuromuscular disorders.

The pelvic tilt is part of a complex deformity in which both the spine and the hip are involved. By viewing the different planes and analyzing the deforming forces, four different types of pelvic tilt in combination with spinal and hip deformities can be identified. In spina bifida patients congenital deformities of the spine may add to the progression of scoliosis. Analyzing our own patients we found that certain types of pelvic tilt can be related to certain neuromuscular diseases. Moreover our results show that the pelvic tilt can be effectively corrected by spinal surgery, whereas no effect of hip surgery could be demonstrated.

Azygos continuation of the inferior vena cava: sonographic demonstration of the renal artery ventral to the azygos vein as a clue to diagnosis.

OBJECTIVE: The purpose of this report is to describe the relationship between the renal artery and the azygos vein in patients with congenital infrahepatic interruption of the inferior vena cava with azygos continuation. CONCLUSION: Using abdominal sonography, we showed that in patients with interruption of the inferior vena cava with azygos continuation, the renal artery is ventral to the azygos vein. Because this malformation is frequently associated with cardiac and situs anomalies, awareness of the anatomic relationship between the renal artery and the azygos vein can aid in diagnosis and may substitute for more expensive and invasive diagnostic procedures.

[Lumbar fusion in adults--dorsal or combined ventral/dorsal approach?]. / Lumbale Fusion bei Erwachsenen--dorsal oder kombiniert ventral/dorsal?

A retrospective study was conducted to compare the results of posterior with combined anterior/posterior lumbar fusion in adults. Seventy-six consecutive posterior cases fused with pedicle screws and 46 combined cases were included and followed for at least 2 years. Subjective assessment was based on the Visual Analogue Scales, Waddel Disability and Impairment Score and the GBB for objective quantification of complaints. Furthermore, a thorough clinical examination was done and X-rays including flexion/ extension radiographs, were taken. Questions were asked about the occupational status as well. Pain decreased significantly more in the combined cases than in the posterior fusion cases. In one case a lesion of the common iliac vein occurred during a retroperitoneal approach. Only about half the patients working preoperatively returned to work again. In conclusion, the benefit of better pain relief after combined fusion must be regarded in relation to a higher complication rate due to a second approach.