1 files changed, 153 insertions, 0 deletions
diff --git a/src/armadillo/include/armadillo_bits/fn_randperm.hpp b/src/armadillo/include/armadillo_bits/fn_randperm.hpp
new file mode 100644
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--- /dev/null
+++ b/src/armadillo/include/armadillo_bits/fn_randperm.hpp
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: Apache-2.0
+// 
+// Copyright 2008-2016 Conrad Sanderson (http://conradsanderson.id.au)
+// Copyright 2008-2016 National ICT Australia (NICTA)
+// 
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+// 
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// ------------------------------------------------------------------------
+
+
+//! \addtogroup fn_randperm
+//! @{
+
+
+
+template<typename obj_type>
+inline
+void
+internal_randperm_helper(obj_type& x, const uword N, const uword N_keep)
+  {
+  arma_extra_debug_sigprint();
+  
+  typedef typename obj_type::elem_type eT;
+  
+  // see op_sort_index_bones.hpp for the definition of arma_sort_index_packet
+  // and the associated comparison functor
+  
+  typedef arma_sort_index_packet<int> packet;
+  
+  std::vector<packet> packet_vec(N);
+  
+  for(uword i=0; i < N; ++i)
+    {
+    packet_vec[i].val   = int(arma_rng::randi<int>());
+    packet_vec[i].index = i;
+    }
+  
+  arma_sort_index_helper_ascend<int> comparator;
+  
+  if(N >= 2)
+    {
+    if(N_keep < N)
+      {
+      typename std::vector<packet>::iterator first    = packet_vec.begin();
+      typename std::vector<packet>::iterator nth      = first + N_keep;
+      typename std::vector<packet>::iterator pastlast = packet_vec.end();
+      
+      std::partial_sort(first, nth, pastlast, comparator);
+      }
+    else
+      {
+      std::sort( packet_vec.begin(), packet_vec.end(), comparator );
+      }
+    }
+  
+  if(is_Row<obj_type>::value)
+    {
+    x.set_size(1,N_keep);
+    }
+  else
+    {
+    x.set_size(N_keep,1);
+    }
+  
+  eT* x_mem = x.memptr();
+  
+  for(uword i=0; i < N_keep; ++i)
+    {
+    x_mem[i] = eT( packet_vec[i].index );
+    }
+  }
+
+
+
+template<typename obj_type>
+arma_warn_unused
+inline
+typename enable_if2< is_Mat<obj_type>::value, obj_type >::result
+randperm(const uword N)
+  {
+  arma_extra_debug_sigprint();
+  
+  obj_type x;
+  
+  if(N > 0)  { internal_randperm_helper(x, N, N); }
+  
+  return x;
+  }
+
+
+
+arma_warn_unused
+inline
+uvec
+randperm(const uword N)
+  {
+  arma_extra_debug_sigprint();
+  
+  uvec x;
+  
+  if(N > 0)  { internal_randperm_helper(x, N, N); }
+  
+  return x;
+  }
+
+
+
+template<typename obj_type>
+arma_warn_unused
+inline
+typename enable_if2< is_Mat<obj_type>::value, obj_type >::result
+randperm(const uword N, const uword M)
+  {
+  arma_extra_debug_sigprint();
+  
+  arma_debug_check( (M > N), "randperm(): 'M' must be less than or equal to 'N'" );
+  
+  obj_type x;
+  
+  if( (N > 0) && (M > 0) )  { internal_randperm_helper(x, N, M); }
+  
+  return x;
+  }
+
+
+
+arma_warn_unused
+inline
+uvec
+randperm(const uword N, const uword M)
+  {
+  arma_extra_debug_sigprint();
+  
+  arma_debug_check( (M > N), "randperm(): 'M' must be less than or equal to 'N'" );
+  
+  uvec x;
+  
+  if( (N > 0) && (M > 0) )  { internal_randperm_helper(x, N, M); }
+  
+  return x;
+  }
+
+
+
+//! @}