From: KevinWilloughby@acm.org.invalid.retro.com   
      
   In article ,   
   azuzek@nospam.accessplus.com.ar.retro.com says...   
   > "Kevin Willoughby"  escribió en   
   > el mensaje news:MPG.1a8260716cac89c6989c25@news.rcn.com...   
   > > In article , invalid@nospam.com   
   > > says...   
   > > > Uhh...i heard something about extensive use of JAVA.   
   > > I'm not quite sure of the extent of "extensive", but yes, Java (not all   
   > > upper-case, please) was one of the many, many tools used on MER.   
   > I would be very surprised to know that the rover itself runs Java code.   
      
   I hate to admit a mistake, but: I've tried to find my original source   
   for this and have to admit that I may have confused some of the Java-   
   based Earth-based support software (e.g., Collaborative Information   
   Portal -- CIP), with the software on the rover itself.   
      
   Sorry about that!   
      
      
   >  I   
   > don't think Java meets the hard real time requirements of the rover   
   > software. For instance, you absolutely need to know how much time each task   
   > will need to complete, but in Java you can't predict when the garbage   
   > collection will run, making the whole system unpredictable.   
      
   Even without garbage collection, most modern computers are   
   unpredictable. Modern computers are quite dependent on a cache for good   
   performance. Many systems have multiple levels of cache. How long it   
   takes to perform a task is a non-trivial statistical computation.   
      
   A lot of research has been done on garbage collection. It is possible to   
   limit the CPU time consumed in garbage collection, allowing a real time   
   system (at the expense of perhaps requiring a bit more memory).   
      
   This kind of software can get complex. "Simpler is better" is a valid   
   philosophy. Yet I wouldn't assume that Java can't be used in real time   
   systems. Note that the very first Java Specification Request   
   (http://www.jcp.org/aboutJava/communityprocess/first/jsr001/,   
   http://www.rtj.org/) is for real-time Java.   
   --   
   Kevin Willoughby         kevinwilloughby@acm.orgNoSpam.invalid   
      
   Imagine that, a FROG ON-OFF switch, hardly the work   
   for test pilots. -- Mike Collins   
      
   --- SoupGate-Win32 v1.05   
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