Wednesday, 24 April 2019

Denormalized Floating Point Numbers Issues

Back in 2013 I wrote a blog post entitled "DSP Tech Brief : Some Notes On Implementing DSP Algorithms - C or Assembly, Fixed or Floating Point" :
Since I wrote that first post I've often thought about writing an update to discuss denormalized floating point numbers. I never got around to it but I recently saw a post that explains the issue perfectly.

Before I get to the specific blog post, a bit of DSP history might help.

Back in the very earliest days of floating point DSPs the silicon manufacturers had the choice of supporting IEEE floating point numbers or not. Supporting IEEE standard floating point numbers sounds like the logical choice however the silicon required to support denormalized numbers without increasing processing time for floating point operations (like general purpose CPUs do) meant that the cost (i.e. number of transistors) of supporting IEEE floating point numbers was far higher than not supporting the standard. Understanding denormalized numbers was key to writing code that could be portable between DSPs that supported them and those that didn't.

Now-a-days most DSPs support IEEE floating point numbers with no run-time overhead for handling denormalized numbers however when the same code is run on a general purpose CPU then the issue of denormalized number support needs to be taken very seriously, to avoid the code becoming very slow.

Now to the excellent summary of the issue of denormalized floating point numbers by Nigel Redmon at EarLevel Engineering :
    The main aricle is :
    And there are some additional useful caveats here :
The best part about Nigel's main article is that it gives some great suggestions about how to avoid these problems.

Further References

Wednesday, 9 January 2019

The Next Round Of The University Of Oxford, UK Digital Signal Processing Courses Take Place In June 2019

As part of the University Of Oxford Summer Engineering Program for Industry, the Digital Signal Processing courses are returning in June 2019, for the 27th year.
The courses are presented by experts from industry for Engineers in industry and over the last 27 years has trained many hundreds of Engineers, from all areas of Science and Engineering.

Here is a summary of the two courses.

Digital Signal Processing (Theory and Application) - Monday 3rd to Wednesday 5th June 2019
This course provides a good understanding of DSP principles and their implementation and equips the delegate to put the ideas into practice and/or to tackle more advanced aspects of DSP. 'Hands-on' laboratory sessions are interspersed with the lectures to illustrate the taught material and allow you to pursue your own areas of interest in DSP. The hands-on sessions use specially written software running on PCs.

Subjects include :

Theoretical Foundations
Digital Filtering
Fourier Transforms And Frequency Domain Processing
DSP Hardware And Programming
ASIC Implementation
Typical DSP Applications

Digital Signal Processing Implementation (algorithms to optimization) - Thursday 6th June 2019

A one-day supplement to the Digital Signal Processing course that takes the theory and translates it into practice.
The course will include a mixed lecture and demonstration format and has been written to be independent of target processor architecture.
The course will show how to take common DSP algorithms and map them onto common processor architectures. It will also give a guide line for how to choose a DSP device, in particular how to choose and use the correct data word length for any application.

Attendee Feedback From Previous Courses :

It was informative, enjoyable and stimulating
Excellent content, very lively thanks to the 2 excellent presenters - Anonymous
A very good introduction to DSP theory
Excellent lecturers! Really useful information and very understandable
Great mix of theory and practice
The lecturers gave a detailed and excellent explanation of the fundamental topics of DSP with real world engineering practice.
This session closes the gap and clears up much confusion between classroom DSP theories and actual DSP implementation.
Very good session, with in-depth discussion on the math and background.

These courses will be held at the University of Oxford, UK

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Evaluate The Numerix-DSP Libraries :