1. Professor Ioana Banicescu CSE 8843
Computational Models
Professor Ioana Banicescu
CSE 8843

2. Architectural Models for Parallel Algorithm Design
Different algorithms require different architectures to solve the same problem efficiently
Need to design a new algorithm for each architecture
To avoid the complexity and cost of software development

3. Universal Abstract Model for Parallel Architecture
Parallel programs can be ported to specific computers
Parallel programs can be written for abstract model
Software development cost is reduced
Performance can be predicted since: parameters (characteristics) of the abstract model vs. those of specific architectures are known

4. Universal Model Characteristics
Sufficiently general to capture the most important properties of a class of parallel computers
Programs designed for this abstract model must execute efficiently on parallel computers
and (2) are conflicting goals.
Observation: The abstract model must make assumptions about the connectivity (degree of connectivity) among processors:
Linear arrays and meshes: low
Hypercubes: high

5. Universal Model Characteristics (continued)
If the abstract model assumes low connectivity, algorithms designed for it will be optimal for parallel architectures with these characteristics and sub- optimal for architectures with high connectivity (i.e. communication resources under-utilized)
Similarly in the case, the abstract model assume high connectivity

6. Universal Model Characteristics (continued)
Regardless of the connectivity of the parallel model, it yields sub-optimal performance for some architectures
Argument against the existence of a universal abstract model: No such model is currently known

7. Today’s Methodology in Parallel Algorithm Design
Design parallel algorithms in terms of basic data communication operations
Only implementation of these operations must be optimized for different parallel computers
Communication operations are a small set
Concurrency vs. Data locality