Kokkos::sort fails for view with all the same values

[mndevec]

Kokkos sort seems to be failing with messages
':0: : block: [0,0,0], thread: [0,93,0] Assertion View bounds error failed.'
when it is run with a view which has its all values exactly same. A simple example is below.

#include <Kokkos_Core.hpp>
#include<Kokkos_Sort.hpp>
#include<Kokkos_Random.hpp>
typedef typename Kokkos::Cuda MyExecSpace;
//typedef typename Kokkos::OpenMP MyExecSpace;

int  main (int  argc, char ** argv){
  Kokkos::initialize( );
  int n = 256;
  typedef Kokkos::View<int*,MyExecSpace> KeyViewType;
  KeyViewType keys("Keys",n);
  Kokkos::fence();
  Kokkos::sort(keys,true);
  Kokkos::fence();
  Kokkos::finalize();

  return 0;
}

Also, the array in the below example somehow triggering a similar error in sort function. Errors occur with openmp as well, if the second argument of sort is provided as true.

#include <Kokkos_Core.hpp>
#include<Kokkos_Sort.hpp>
#include<Kokkos_Random.hpp>
typedef typename Kokkos::Cuda MyExecSpace;
//typedef typename Kokkos::OpenMP MyExecSpace;
int myarray[] = {18364,19072,18320,19734,19955,23360,21902,22788,21859,23628,22744,24204,26327,24912,26460,28053,25575,27168,27213,27922,28805,31638,31593,32522,29469,34470,36509,33009,34426,37880,37171,40641,40649,37788,40525,39105,40634,38401,40758,39329,40678,38952,37896,38600,38604,40570,38633,38540,39295,39405,41302,42305,41977,42765,44898,44998,45015,42213,41722,42107,41596,44089,43511,43113,46179,46459,45099,45119,45431,46487,45395,45334,48295,46730,48315,48279,45706,46111,47437,48214,47839,47607,46769,46775,47247,47484,45693,49230,52616,49275,49784,50613,49647,50458,50492,50446,50580,51908,51154,53472,53464,53545,53561,53605,56288,53589,53513,54164,60713,66319,69563,67439};

int  main (int  argc, char ** argv){

  Kokkos::initialize( );
  typedef int KeyType;
  typedef Kokkos::View<KeyType*,MyExecSpace> KeyViewType;

  int n = 112;
  KeyViewType keys("Keys",n);

  auto h_keys = Kokkos::create_mirror_view (keys);
  for (int i = 0; i < n; ++i){
   h_keys(i) = myarray[i];
  }
  Kokkos::deep_copy(keys,h_keys);
  Kokkos::fence();
  Kokkos::sort(keys,true);

  Kokkos::finalize();

  return 0;
}

[mndevec]

For the second issue, it seems that it has nothing to do with the array values. The views that have lengths of 112 and 56 are causing Kokkos::sort to fail.

[crtrott]

Ok I saw what happens, the automatic determination of the range of values comes back with the range is null. The inverse of it (which is used in the index calculations) comes back as inf. This particular error can only happen if all values are the same. I mark this as a bug and we'll put it in the next milestone.

[mndevec]

Thank Christian,
Were you able to reproduce the second issue?

[crtrott]

I pushed a fix which makes both examples work. I also added a unit test for the "all keys are the same" situation.