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Per Westermark
01/19/12 07:43
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Msg Score: -1
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#185565 - Understanding the mapping important
Responding to: Erik Malund's previous message
Erik Malund said:
if you need to "understand the efficiency" you should not use C in the first place

I don't agree.

Being able to understand the efficiency of the compiler and how language constructs maps to processor instructions gives you options when writing C/C++ code.

For trivial things, the compiler can convert integer multiply of 2 with a shift. But think about 8051 and pointers. When you do know the limitations the 8051 chip has when using indirect addresses, you can focus on designing without pointers or at least with no more pointers than the compiler can manage to map to index registers in the processor.

Code bloat is often the result of people not knowing what is cheap and what is expensive, when they write their C/C++ program.

It is only by knowing the mappings performed that you can know that for one processor, recursion is basically no-cost, allowing very clean code to run efficiently. While you on the 8051 probably need to store explicit state information in a table - a manually administered stack.

List of 49 messages in thread
TopicAuthorDate
interfacing with 93c66      Anil Kumar      01/14/12 01:04      
   Interfacing AT93CXXX Serial EEPROMs with AT89LP MCUs      Jan Waclawek      01/14/12 04:20      
      Direct Links      Michael Karas      01/14/12 11:04      
   interfacing ith93c66      Anil Kumar      01/16/12 03:09      
      Better Learn Both      Michael Karas      01/16/12 18:01      
      How about the 8051 code library?      Neil Kurzman      01/16/12 23:30      
         interfacing with 93c66      Anil Kumar      01/18/12 22:51      
            An exercise for the reader      David Prentice      01/19/12 01:20      
               interfacing with 93c66      Anil Kumar      01/19/12 22:59      
      Then you need to learn...      Robert Revens      01/19/12 05:34      
         I disgaree        David Prentice      01/19/12 06:25      
            cheap fatty sausage      Erik Malund      01/19/12 07:04      
               Understanding the mapping important      Per Westermark      01/19/12 07:43      
                  out of context      Erik Malund      01/19/12 09:13      
                  So exactly what was the disagreement???      Per Westermark      01/20/12 02:52      
                     I agree with you      David Prentice      01/20/12 03:55      
                        Don't simplify to believe it's about fastest speed      Per Westermark      01/20/12 05:27      
                        again      Erik Malund      01/20/12 07:48      
                     true      Erik Malund      01/20/12 07:42      
               Are you serious?      David Prentice      01/19/12 08:15      
                  also out of context      Erik Malund      01/19/12 09:16      
               Missing the point!      Andy Neil      01/19/12 12:19      
                  the full monte      Erik Malund      01/19/12 12:37      
   interfacing with 93c66      Anil Kumar      01/26/12 21:56      
      And your work      Per Westermark      01/27/12 02:46      
      plz check it      Andy Neil      01/27/12 06:58      
      ,sometimes you have to be VERY specific      Erik Malund      01/27/12 07:31      
      wrong strategy and many errors      Stefan KAnev      01/30/12 04:12      
   interfacing with 93c66      Anil Kumar      01/28/12 03:16      
      why do you resist using external ram?      Erik Malund      01/28/12 08:58      
         interfacing with 93c66      Anil Kumar      01/29/12 02:21      
            Payed support not good enough?        Per Westermark      01/29/12 03:18      
               interfacing with 93c66      Anil Kumar      01/29/12 22:29      
                  Any Specific Reason for using...      Maunik Choksi      01/29/12 23:09      
                     interfacing with 93c66      Anil Kumar      01/29/12 23:33      
                        please explain      Andy Neil      01/30/12 14:39      
                        It is advisable to use alternate available....      Maunik Choksi      01/30/12 22:37      
                           interfacing with 93c66      Anil Kumar      01/31/12 22:06      
                              Can you elaborate it ?      Maunik Choksi      01/31/12 22:44      
                                 interfacing with 93c66      Anil Kumar      01/31/12 22:51      
                                    You give me your email-id      Maunik Choksi      01/31/12 22:53      
                                       email id      Anil Kumar      01/31/12 22:57      
                                          Ok      Maunik Choksi      01/31/12 22:58      
                  Wrong - you are just not responding to on-topic questions      Per Westermark      01/30/12 03:00      
                  you've got plenty of suggestions      Erik Malund      01/30/12 06:53      
                     Off-topic but Siemens/seconds...      Per Westermark      01/30/12 08:04      
                     funny result      Erik Malund      02/02/12 09:20      
                        Output      Per Westermark      02/02/12 15:14      
   still waiting      Erik Malund      02/01/12 06:49      

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