Hello ! I have a problem which I can't resolve. I wrote program for 89C2051 for one of my friend in Basom Basic compiler (http://www.mcselec.com). Compiled code was about 1945 bytes. Since I prefer C, I transalte Bascom basic to C. But when I compile, generated code was 2313. I try to change optimization parameters, but generated code never go below 2313. Even bigger. Where am I wrong ? Is it possible that stupid Basic make smaller code tne best C compiler ? Then I find out that this code: while (1) { printf ("Hello World\n"); } generate fully 1093 bytes (!) for Atmel 89C2051. 1093 bytes???? Three lines? Same program in Bascom generate only 154 (!) bytes. When I remove all "printf" from my C code, generated code was arond 2200 byte. But, with same action in Basic code (remove all "print") 1340 bytes long code. Exactly same program in Keil C and Bascom basic generate 860 byte smaller code ! I don't belive this. Do I have to program in (stupid) Basic if I want smaller code ? I still belive I did mistake somewhere, so I need help. I will send both C and basic code for interested people. With best regards !
"And...with linker code packing... Keil (using putchar and puts and linker code packing): Code Size: 486 Bytes Execution Speed: 6.330105 Seconds" Jon, That's very interesting. What optimisation level did you use? Stefan
Erik, "but you come across as a "if it is too slow buy a faster (more expensive) processor, do not try to streamline the code, it may make it not proper" person" Not at all. Most of the 8051 stuff I work on is battery powered. Power consumption is of paramount importance - we use very low clock speeds and keep the CPU in idle mode >95% of the time. Maximum code space is 16k. Some aspects of data acquisition and output require very accurate timing. I spend a considerable amount of time making code as efficient as possible both in terms of speed and size. I don't use an RTOS - but I wouldn't hesitate to do so if it were beneficial to the project and feasible in terms of size and speed. I don't use C++ - but again I would readily do so given the above provisos. The constraints of the operating environment mean that we have to use a microcontroller rather than a microprocessor. The software needs to do a lot of complex floating point maths and give formatted output via the serial port. It achieves all this in a timely and efficient manner using printf() and the Keil floating point library. The microcontroller turns out to be perfectly suitable for a job that you seem to think is only suited to a microprocessor. My point is really this: If tools are available that are beneficial to the project then use them. Don't rule things out merely because you've decided at some time that they are not appropriate. There is no absolute divide between controllers and processors in much the same way that there is no absolute divide between what is and is not suitable for use on each device. Stefan
"Where is the swith for linker code packing?" It's in the "Options for target" -> "C51" tab. Stefan
Nice job comparing SIEVE in both compilers. You now know whay I did the first post. But I didn't measere execution time. Where is the swith for linker code packing ? I make another threed post, where I looking Libraries for smart cards (eg. SLE4428). Anyoone help since this is most 'live' thread ? Mladen Bruck
Dave, I can't see anything wrong with Hans's description. What he describes happens at compile time. His third point was that if the compiler sees a non-constant string anywhere in the code, then it gives up trying to optimise, and uses the full-featured version of printf(). Hmmm.. okay, I went back and re-read the post that I (somewhat snippily) replied to, and I agree that it's technically possible. However, this feels like something that should be taken into account and compensated for (if necessary) on the application side rather than the tools side. If you start building this level of "special case" consideration into the toolset, you'll wind up with Win51, the first 32-bit (!) GUI OS for embedded 8051 applications, and I, for one, would rather skip that particular nightmare. Not to mention the extra development effort and cost and the price point impact it would no doubt have. IMHO, of course. You could also argue that this is the whole point of having an optimizer. It's late. I give up. =) - Dave
Jon, Here's a suggestion for the manual. How about adding a note to the printf page, pointing out that puts/putchar use much less code memory for simple output.
And...with linker code packing... Keil (using putchar and puts and linker code packing): Code Size: 486 Bytes Execution Speed: 6.330105 Seconds Jon
I just downloaded the BASCOM demo and played around for a while. It's pretty neat. After playing around for a while, I decided to run a real program and compare it to C51. Not wanting to spend the rest of my life on this, I chose the SIEVE. Here are the results: BASCOM: Code Size: 866 Bytes Execution Speed: 23.553726 Seconds Keil (using printf): Code Size: 1,248 Bytes Execution Speed: 6.331546 Seconds Keil (using putchar and puts): Code Size: 524 Bytes Execution Speed: 6.330123 Seconds I did all speed testing with the uVision2 Debugger/Simulator under identical circumstances. From this little comparison, I think you can tell that the printf is what kills the C code--but not the performance. And, the difference between a CUSTOM formatter (using puts and putchar) and printf saves 724 bytes. I'll be more than happy to post the source for these things (of course, the SIEVE source comes with the Keil tools) if anyone wants to check my work. Jon
You can get into situations where, for example, if there are multiple source files, each source module calls for a different "edition" of printf. If this is the case, it is actually up to the linker to resolve which printf gets included. It's fairly easy for the compiler to say, "Oh, this module calls printf and only has an unsigned int in the format string. OK, include printf#1." In another module, however, the compiler might say, "Oh. this module calls printf and uses floating-point format specifiers in the format string (but no unsigned ints are used). OK, include printf#4." Now, the linker has to make sense of all of these different printf functions. And, at the end of the day, the linker includes most of what's in the standard printf. The only applications this would work well for would be the Hello World example. I mean, if I include sprintf in my application, I'm going to use it to my best advantage. I'm not going to try to use a printf SUBSET to save memory. If memory is that precious, I'm going to write my own formatting routines. printf has been an acknowledged memory hog since C was invented. There have been very few successful attempts at reducing its size. For its size, I think it does quiet well. Jon
Dave, I can't see anything wrong with Hans's description. What he describes happens at compile time. His third point was that if the compiler sees a non-constant string anywhere in the code, then it gives up trying to optimise, and uses the full-featured version of printf().
The method how to handle non-constant format strings is obvious, isn't it? Apparently, not obvious enough. The mechanism that you outline is suitable for an interpreted language, but a compiled application has to be self-sufficient. The app can not, at run time, upon encountering a foreign format specifier, ask the compiler for anything. - Dave
You can write bloated code in any language, including assembly. I agree; however it is a characteristic of "real programmers" as opposed to "embedded programmers" to concentrate on the elegance (in their opinion) and state of the art of the code rather than the efficiency. I consulted for a while with a major cellphone company and the "real programmers" decided to go to C++. This led to the need to double the clockspeed of the processor. Before this happened I said, wrote and almost screamed "faster clock is more battery usage and one of the problems we have is is battery charge life". They went ahead anyhow "because it is the right thing to do" and now the lack of battery life has led to a sharp decline in sales for that company. Erik
You can write bloated code in any language, including assembly. You can write "efficient" code in C, and yes, even in C++ -- if you know what you're doing. C++ in particular is more subtle and thus more difficult than it seems on casual inspection. The smallest overall program is not necessarily one where individual basic blocks are the smallest.
Stefan, Nothing personal, but you come across as a "if it is too slow buy a faster (more expensive) processor, do not try to streamline the code, it may make it not proper" person. We are discussing the difference between a microcontroller and a microprocessor related to purpose, use, functionality and application. I have worked with "real C" programmers and they professed that there was no need whatsoever to understand the purpose of the equipment such as no C++ for low cost or ultrafast response. I once revised a development where a bloated RTOS with some "real C" code bugged the processor so far down that the "real C programmer" suggested a change to an ARM processor. It took about a month to get the bloatings out of the code (still using C) and then the '51 was more than sufficient. Re C++ you need to read this interview http://www.ganssle.com/tem/tem17.pdf Trevlig kvaell Erik
"relatively high? what about efficient" 'C' is relatively efficient. What's your point? "The next we will see is "just add a megabyte of ROM and you can do the proper thing and use C++"" You already can use C++ without adding a megabyte of ROM. Perhaps you should try it? Stefan
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