CRPC-TR95508-S:  Accessing Sections of Out-of-Core Arrays Using an 
Extended Two-Phase Method

Rajeev Thakur, Alok Choudhary

January 1995

Of the authors listed above, please indicate which are:

  Minority authors:

  Female authors:    

  Student authors:  Rajeev Thakur

Keywords (list up to 8):

Parallel I/O, Runtime Support, Out-of-Core Computations, I/O Optimizations

In out-of-core computations, data needs to be moved back and forth 
between main memory and disks during program execution. In this paper, we 
propose a technique called the Extended Two-Phase Method, for accessing 
sections of out-of-core arrays efficiently. This is an extension and 
generalization of the Two-Phase Method for reading in-core arrays from 
files, which was previously proposed in [Rosario93,Bordawekar93]. The 
Extended Two-Phase Method uses collective I/O in which all processors 
cooperate to perform I/O in an efficient manner by combining  several I/O 
requests into fewer larger requests, eliminating multiple disk accesses 
for the same data and reducing contention for disks. We describe the 
algorithms for reading as well as writing array sections. Performance 
results on the Intel Touchstone Delta for many different access patterns 
are presented and analyzed.  It is observed that the Extended Two-Phase
Method gives consistently good performance over a wide range of access
patterns.  


Publication History:

  Submitted to: Int. Conf. on Parallel Processing (ICPP), 1995

  Published in: 

  Also available as NPAC Technical Report SCCS-685, Syracuse University