From: daniel.kruegler@googlemail.com   
      
   Am 29.04.2012 22:09, schrieb Peter Liedermann:   
   > My free profiler "Very Sleepy", which has been of great use to me,   
   > points me to the following, which is not my code and therefore   
   > presumed to be STL-implementation. (VC++ 11, presumably Dinkum)   
   >   
   > void clear()   
   > 0.16s { // erase all   
   > 0.08s erase(begin(), end());   
   > 0.00s }   
   >   
   > Question: Why does it perform this erase as part of clear(), can I   
   > keep it from doing so and how? I see no point in erasing for a vector   
   > . As far as I remember what I have read, there should not   
   > be any erasing in this case. The (logical) length of the vector   
   > should be adjusted (constant complexity) and the old contents are left   
   > as garbage.   
      
   The implementation you are observing, is conforming, because the   
   standard describes above semantics. Nonetheless you are right: A good   
   quality-implementation can skip the iteration here and can simply adjust   
   the internal length representation via an O(1) step. I'm pretty sure   
   that gcc 4.8 does this, for example, if the value type of the vector has   
   a trivial destructor.   
      
   > Could I be better off using old C arrays?   
   >   
   > Any hint greatly appreciated, this is really a hotspot in my program.   
      
   This is really an quality-of-implementation issue, you should ask your   
   vendor for improvements, bringing the hot-spot situation as an example.   
      
   HTH & Greetings from Bremen,   
      
   Daniel Krügler   
      
      
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