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 /*
 Copyright 2010-2011, D. E. Shaw Research.
 All rights reserved.
  
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are
 met:
  
 * Redistributions of source code must retain the above copyright
   notice, this list of conditions, and the following disclaimer.
  
 * Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions, and the following disclaimer in the
   documentation and/or other materials provided with the distribution.
  
 * Neither the name of D. E. Shaw Research nor the names of its
   contributors may be used to endorse or promote products derived from
   this software without specific prior written permission.
  
 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
  
 #ifndef ROCRAND_THREEFRY4_IMPL_H_
 #define ROCRAND_THREEFRY4_IMPL_H_
  
 #include "rocrand/rocrand_common.h"
 #include "rocrand/rocrand_threefry_common.h"
  
 #include <hip/hip_runtime.h>
  
 #ifndef THREEFRY4x32_DEFAULT_ROUNDS
     #define THREEFRY4x32_DEFAULT_ROUNDS 20
 #endif
  
 #ifndef THREEFRY4x64_DEFAULT_ROUNDS
     #define THREEFRY4x64_DEFAULT_ROUNDS 20
 #endif
  
 namespace rocrand_device
 {
  
 template<typename state_value, typename value, unsigned int Nrounds>
 class threefry_engine4_base
 {
 public:
     struct threefry_state_4
     {
         state_value  counter;
         state_value  key;
         state_value  result;
         unsigned int substate;
     };
     using state_type        = threefry_state_4;
     using state_vector_type = state_value;
  
     __forceinline__ __device__ __host__
     void discard(unsigned long long offset)
     {
         this->discard_impl(offset);
         this->m_state.result = this->threefry_rounds(m_state.counter, m_state.key);
     }
  
     __forceinline__ __device__ __host__
     void discard_subsequence(unsigned long long subsequence)
     {
         this->discard_subsequence_impl(subsequence);
         m_state.result = this->threefry_rounds(m_state.counter, m_state.key);
     }
  
     __forceinline__ __device__ __host__
     value operator()()
     {
         return this->next();
     }
  
     __forceinline__ __device__ __host__
     value next()
     {
 #if defined(__HIP_PLATFORM_AMD__)
         value ret = ROCRAND_HIPVEC_ACCESS(m_state.result)[m_state.substate];
 #else
         value ret = (&m_state.result.x)[m_state.substate];
 #endif
         m_state.substate++;
         if(m_state.substate == 4)
         {
             m_state.substate = 0;
             m_state.counter  = this->bump_counter(m_state.counter);
             m_state.result   = this->threefry_rounds(m_state.counter, m_state.key);
         }
         return ret;
     }
  
     __forceinline__ __device__ __host__
     state_value next4()
     {
         state_value ret = m_state.result;
         m_state.counter = this->bump_counter(m_state.counter);
         m_state.result  = this->threefry_rounds(m_state.counter, m_state.key);
  
         return this->interleave(ret, m_state.result);
     }
  
 protected:
     __forceinline__ __device__ __host__
     static state_value threefry_rounds(state_value counter, state_value key)
     {
         state_value X;
         value       ks[4 + 1];
  
         static_assert(Nrounds <= 72, "72 or less only supported in threefry rounds");
  
         ks[4] = skein_ks_parity<value>();
  
         ks[0] = key.x;
         ks[1] = key.y;
         ks[2] = key.z;
         ks[3] = key.w;
  
         X.x = counter.x;
         X.y = counter.y;
         X.z = counter.z;
         X.w = counter.w;
  
         ks[4] ^= key.x;
         ks[4] ^= key.y;
         ks[4] ^= key.z;
         ks[4] ^= key.w;
  
         /* Insert initial key before round 0 */
         X.x += ks[0];
         X.y += ks[1];
         X.z += ks[2];
         X.w += ks[3];
  
         return rounds_4<state_value, value, Nrounds>(X, ks);
     }
  
     __forceinline__ __device__ __host__
     void discard_impl(unsigned long long offset)
     {
         // Adjust offset for subset
         m_state.substate += offset & 3;
         unsigned long long counter_offset = offset / 4;
         counter_offset += m_state.substate < 4 ? 0 : 1;
         m_state.substate += m_state.substate < 4 ? 0 : -4;
         // Discard states
         this->discard_state(counter_offset);
     }
  
     __forceinline__ __device__ __host__
     void discard_subsequence_impl(unsigned long long subsequence)
     {
         value lo, hi;
         ::rocrand_device::detail::split_ull(lo, hi, subsequence);
  
         value old_counter = m_state.counter.z;
         m_state.counter.z += lo;
         m_state.counter.w += hi + (m_state.counter.z < old_counter ? 1 : 0);
     }
  
     __forceinline__ __device__ __host__
     void discard_state(unsigned long long offset)
     {
         value lo, hi;
         ::rocrand_device::detail::split_ull(lo, hi, offset);
  
         state_value old_counter = m_state.counter;
         m_state.counter.x += lo;
         m_state.counter.y += hi + (m_state.counter.x < old_counter.x ? 1 : 0);
         m_state.counter.z += (m_state.counter.y < old_counter.y ? 1 : 0);
         m_state.counter.w += (m_state.counter.z < old_counter.z ? 1 : 0);
     }
  
     __forceinline__ __device__ __host__
     static state_value bump_counter(state_value counter)
     {
         counter.x++;
         value add = counter.x == 0 ? 1 : 0;
         counter.y += add;
         add = counter.y == 0 ? add : 0;
         counter.z += add;
         add = counter.z == 0 ? add : 0;
         counter.w += add;
         return counter;
     }
  
     __forceinline__ __device__ __host__
     state_value interleave(const state_value prev, const state_value next) const
     {
         switch(m_state.substate)
         {
             case 0: return prev;
             case 1: return state_value{prev.y, prev.z, prev.w, next.x};
             case 2: return state_value{prev.z, prev.w, next.x, next.y};
             case 3: return state_value{prev.w, next.x, next.y, next.z};
         }
         __builtin_unreachable();
     }
  
 protected:
     threefry_state_4 m_state;
 }; // threefry_engine4_base class
  
 } // end namespace rocrand_device
  
 #endif // ROCRAND_THREEFRY4_IMPL_H_