[LLVMdev] llvm::DenseSet with reverse iterator (original) (raw)

Vassil Vassilev vvasilev at cern.ch
Thu Jul 12 10:43:59 PDT 2012

Hi, Thanks a lot for the help! It seems that the SmallSetVector is the ADT I need (interface-wise). Is more efficient than llvm::UniqueVector? In my use case I have to insert a new element in the structure only if the element is unique. I hardly expect more than 32 elements. Do you think I gain a lot if I use the SmallSetVector instead of using SmallVector + slow searching on every push_back? Vassil On 7/12/12 6:23 PM, Michael Ilseman wrote:

Something that might interest you is the SetVector, which as its name implies is both a set and a vector paired together. You get the advantage of doing set-like operations (search) on the set and vector-like operations (iteration, random access) on the vector, but at the cost of paying the price for both data structures when modifying the structure (and double the memory). This seems like it might be more heavy-weight than you needed, but it might serve your purposes. The iteration order is the insertion order; if you want some other ordering and stronger iterators, you might have to consider std::set.

[1] http://llvm.org/doxygen/SetVector8hsource.html [2] http://llvm.org/docs/ProgrammersManual.html#dsssetvector On Thu, Jul 12, 2012 at 10:04 AM, Owen Anderson <resistor at mac.com> wrote: Reverse iteration doesn't really make sense for DenseSet, since its iteration order isn't meaningful to begin with...

--Owen On Jul 12, 2012, at 8:20 AM, Vassil Vassilev wrote:

Hi, I need a data structure which has fast search and I can walk it forward and backward. Is there something like that in LLVM ADT which am not aware of? And if not can I implement it in llvm::DenseSet? Vassil

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