next up previous contents index
Next: Performance Bottlenecks in the Up: Performance Evaluation Previous: Determine Whether Reasonable Performance

Identify Performance Bottlenecks


The formulas mentioned in section 5.3.3, in addition to providing an estimate of performance, can help one identify whether the performance is limited by computation, by the number of messages, or by the volume of communication. Even if the estimate is far from correct, the user may get some information about the performance bottleneck by studying the computation and communication estimates provided by those formulas.

Comparing the execution times of a problem of size N and one of size N/2 may also provide insight into the performance of the ScaLAPACK routine being used. Let tex2html_wrap_inline12212 and tex2html_wrap_inline12220 be the time required for a problem of size N and size N/2, respectively, on P processors.

This performance analysis suggests which computer characteristic is most likely limiting the performance. It cannot say whether one is getting good performance.

Susan Blackford
Tue May 13 09:21:01 EDT 1997