1. Getting serious about “going fast” on the TigerSHARC
What are the characteristics of DSP algorithms?

2. DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada
Tackled today
What are the basic characteristics of a DSP algorithm?
A near perfect “starting” example
DCRemoval( ) has many of the features of the FIR filters used in all the Labs
Testing the performance of the CPP version
First assembly version – using I-ALU operations – testing and timing
Code will be examined in more detail in the next lecture
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

3. IEEE Micro Magazine Article
How RISCy is DSP? Smith, M.R.; Micro, IEEE  ,Volume: 12 , Issue: 6 , Dec Pages:
Available on line via the library “Electronic web links”
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

4. Characteristics of an FIR algorithm
Involves one of the three basic types of DSP algorithms
FIR (Type 1), IIR (Type 2) and FFT (Type 3)
Representative of DSP equations found in filtering, convolution and modeling
Multiplication / addition intensive
Simple format within a (long) loop
Many memory fetches of fixed and changing data
Handle “infinite amount of input data” – need FIFO buffer when handling ON-LINE data
All calculations “MUST” be completed in the time interval between samples
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

5. Comparing IIR and FIR filters
Infinite Impulse Response filters – few operations to produce output from input for each IIR stage
Finite Impulse Response filters – many operations to produce output from input. Long FIFO buffer which may require as many operations
As FIR calculation itself.
Easy to optimize
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

6. DCRemoval( ) part of SDR My version
Memory intensive Addition intensive
Loops for main code
FIFO implemented as circular buffer
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

7. DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada
Memory intensive Addition intensive
Loops for main code
FIFO implemented as circular buffer
Not as complex as FIR, but many of the same requirements
Easier to handle
You use same ideas in optimizing FIR over Labs 2 and 3
Two issues – speed and accuracy. Develop suitable tests for CPP code and check that various assembly language versions satisfy the same tests
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

8. E-TDD format of DCRemoval( ) perhaps a little unsophisticated
Clear the internal buffer
Put in one known value with known result (based on MY implementation
If algorithm works for long enough then gives the correct answer
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

9. DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada
First attempt – “ENCM415 approach” Use the integer ALU operations (I-ALU)
Why?
Looks less complex that other options
Learn one thing at a time
Can be done “using direct translation of C++ (working code)
Tests
1) Can we call and return from the assembly code routine? – understanding the C++ calling conventions
2) Does the assembly code routine give the same result as the C++ version?
3) How does the assembly code routine’s performance compare to the C++ version?
and hidden (IMPLICIT) test – are there any errors in jumping backwards and forwards between C++ and many assembly code routines – detailed understanding of the C++ calling conventions
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

10. DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada
Call and return test
Basically – if the code gets here it is probably that we did not crash the system
I use a cut-and-paste approach to develop code variants. This test is (embarrassingly) useful.
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

11. Initially we expect the code to fail to work correctly
If the code works initially, then it is doing so by accident
Use
XF_CHECK_EQUAL( )
Expected to fail
NOTE: This test is just a “cut-and-paste” version of C++ test
with three changes of function name
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

12. DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada
Timing test
Initially – since all we do is “call and return” -- we expect (trivially) fast code
Issues
Some algorithms may optimize better when called many times – cache and coding issues
Does it matter whether the function is called once, 10 or 100 times?
Call the function to test within a loop – make sure that the loop overhead for calling the function does not compromise the timing of the test – may be important if we develop very optimized code, and every last cycle (between interrupts) counts
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

13. DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada
Timing test
Once
10 times
100 times
Normalized the timing tests to “process the function once”
Need to develop various other routines to make tests work -- DoNothing loop, run C++ and assembly code routines in a loop
May not be correctly performing timing – but gives initial concepts
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

14. Other functions needed to run the test
Do Nothing Careful – may be optimized to “nothing”
C++ function loop
J-ALU function loop
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

15. Steps -- Manual technique
Add tests to project
Build connect file so that tests will be activate
Note file name
and directory
name
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

16. Steps -- E-TDD Gui technique
Add tests to project
Build connect file so that tests will be activate
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

17. DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada
Build and run the code
Build and run manually
BUILD PROJECT and DEBUG | RUN
Or build and run using E-TDD GUI
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

18. Use build failure information to determine assembly code function name
Required name for void DCremovalASM_JALU(int *, int *)
_DCremoval_JALU__FPiT1
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

19. Write ASM “call-and-return”, then run the test
Simple ASM stub
GHOST BREAKPOINT – A break point that is set in the code “some how” – completely random, but seems to occur after making big changes in a project – number of ways of handling them
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

20. Proper test run and exit – lib_prog_term
Yellow indicates that there are NO failures but some expected failures
All successes and failures shown in console window
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

21. DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada
Quick look at the code
Will examine in more detail in next class void DCremovalASM(int *, int *)
Setting up the static arrays
Defining and then setting pointers
Moving incoming parameters in FIFO
Summing the FIFO values
Performing (FAST) division
Returning the correct values
Updating the FIFO in preparation for next time this function is called – discarding oldest value, and “rippling” the FIFO to make the “newest” FIFO slot empty
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

22. Developing the assembly code static arrays – “section data1”
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

23. DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada
Define the (250) register names for code maintainability (and marking) ease
Actual static array declaration DEFINE pointers into arrays
DEFINE temps
DEFINE Inpars SET pointers into arrays
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

24. DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada
Key and common error
Same as in C++
There is a difference between
Defining / declaring the pointer register
and
Placing (setting) a value in the pointer register so it actually points some where
Register names – what they are and where they are stored.
In an exam, use of a register in this format is “required” but it is preferred, rather than required, that you include the define statements – watch for question wording
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

25. DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada
Value into FIFO buffer
RISC processor LOAD and STORE architecture
MIPS-like (ENCM369) rather than CISC (ENCM415)
Read from memory  register  store to memory
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

26. DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada
Perform sum
Hardware loops, some 64-bit and some 32-bit instructions
Sum
Division
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

27. Correcting INPARS and then updating the FIFO buffer
Adjust the INPARS remember int *
Update FIFO memory using load / store approach
SLOW
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

28. Adjust tests for expected success
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada

29. DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada
Tackled today
What are the basic characteristics of a DSP algorithm?
A near perfect “starting” example
DCRemoval( ) has many of the features of the FIR filters used in all the Labs
Testing the performance of the CPP version
First assembly version – using I-ALU operations – testing and timing
Code will be examined in more detail in the next lecture
2/19/2019
DC removal Lecture 1, M. Smith, ECE, University of Calgary, Canada