Page 32 - DCAP608_REAL TIME SYSTEMS

Unit 2: Introduction to Real-time Applications

function used in the interpolation is added to calculate the intensity and phase of the Notes
corresponding output pixel. This computation cannot be expressed well using VSIPL++
primitives.
To improve performance, CodeSourcery used a VSIPL++ API extension available in
Sourcery VSIPL++ called “user-defined kernels.” User-defined kernels allow the developer
to write a high-performance computational kernel and still leverage the data-handling
aspects of the VSIPL++ library. A hand-coded kernel with 208 lines of code speeds up
interpolation from 4.23 seconds to 0.18 seconds, an improvement of more than 23 times
that of the original implementation.

On Xeon, the final optimized code runs more than 82 times faster than the C reference
implementation. On the Cell/B.E., it was 5.7 times faster than on the Xeon and more than
1,400 times faster than the reference C code. Even modest, easy-to-implement changes can
significantly improve performance.
Combining performance, productivity, and portability with VSIPL++.

Using a library implementing the open-standard VSIPL++ API made possible the
development of a complex application in far fewer lines of code than are necessary in C.
Out of the box, this code outperformed the C reference implementation. With limited
changes to address performance bottlenecks, performance was further enhanced. And the
application remained portable across vastly different architectures.
Questions:
1. Discuss the main hindrances in developing high-performance radar applications
using the VSIPL++ API.
2. What are the different measures adopted to overcome such problems?

Source: http://mil-embedded.com/articles/case-applications-using-vsipl-api/

2.5 Summary

 Real-time systems have of late, found applications in wide ranging areas.
 Errors due to A/D and D/A conversion as well as due to limited length word calculations.

 It is not meaningful to talk about guarantying real-time performance.
 Software developing is prone to errors.
 Controllers are usually systematized in a hierarchy.
 Higher level controllers and multiple control loops supervise the behaviour of low-level
controllers.
 The term real-time refers to systems in which the correctness of the system depends not
only on the logical result of computation, but also on the time at which the results are
produced.
 Examples of real-time systems include command and control systems, process control
systems, flight control systems, and so on.
 Digital signal processing systems analyse, produce, and transform discrete-time signals.
 A discrete-time signal is a function that is defined only at a particular set of values of time.

 Industrial applications constitute a major usage area of real-time systems.
 A cellular system usually maps a city into cells.

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