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>Hi, > > Can anyone give me typical performance comparision of for Analog Devices >Software Tools for ADSP-218x platform. > > MIPS of a Cross compiled assembly program Vs MIPS of Optimized Hand Written >assembly program? > >Typical example : for any ITU series Speech codecs. > >Hari V Hari, this is a typical "it depends" question. There are many factors that determine cycle count for any given algorithm (the MIPS rate is constant and depends on your hardware). Using the assembly libraries from ADI, you are likely to have very optimized code, which propably cannot be compacted much further. If you can compile (pun intended ;) your program exclusively from library functions, all you have is the C overhead (handling stack and heap, loading pointers, additional register loading and storing, C function calling) in the main loop, but this is negligible compared to calculating an FIR, multiple-section IIR or an FFT, especially on today's fast DSPs. The more complex your program gets, the larger becomes the relation between overhead to processing. There are two main reasons for this: 1. When you program in assembler, you are used to a much leaner programming style (eg. using several bits in one word as flags instead of several words, using predicated instructions instead of conditional branching, vector based programming vs. structured programming, direct hardware drivers, etc.) as compared to higher-level programming. One also has direct access to all registers (and for the SHARC, these are usually enough to reserve index registers for certain tasks), and one can organize multiple instruction computes and parallel data store / loads, which the C compiler usually ignores completely. 2. Even when using exactly the same program structure (for example when compiling a C program to assembler), the assembler code can _always_ easily be optimized, because a compiler is a very general function (having to be able to compile all possible programs), and there are always details which can be coded in way better suited for a specific problem. So if you have to make your own code, that is, you use functions which are not available in the pre-compiled libraries, and you are using many loops, conditional statements, lots of arithmetic, special filter functions, ie. you are making _complex_ code, that's when assembler starts getting ahead of C. Also, for these complex programs, the C code explodes in size, which might require you to store code in external RAM segments, something I never used in my whole career as an assembler DSP programmer (and I believe I haved programmed some pretty wicked applications). Executing code from external RAM (depending on RAM type) can turn your SHARC into a GUPPY. The points is: you _can_ program efficiently in C, if you know your hardware (however, the same person can always generate more efficient assembler code). The problem is, if you program in C _because_ you don't know the hardware (hardware independency is the reason for having higher-lever programming languages in the first place), you will usually end up needing more and faster processors. You have to decide which costs more: more capable hardware or the time it takes you to get into assembler coding. Regards, Andor Bariska WEISS ENGINEERING LTD. - Professional Digital Audio Products Florastrasse 42 8610 Uster Switzerland phone: +41 1 940 20 06, fax: +41 1 940 22 14 mailto: web: http://www.weiss.ch You *can* afford the best |
AW: Third party compilers for ADSP family
Started by ●September 15, 2000
