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 #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<class value>
 __forceinline__ __device__ __host__ int threefry_rotation_array(int indexX, int indexY) = delete;
  
 template<>
 __forceinline__ __device__ __host__ int threefry_rotation_array<unsigned int>(int indexX,
                                                                               int indexY)
 {
     // Output from skein_rot_search: (srs-B128-X5000.out)
     // Random seed = 1. BlockSize = 64 bits. sampleCnt =  1024. rounds =  8, minHW_or=28
     // Start: Mon Aug 24 22:41:36 2009
     // ...
     // rMin = 0.472. #0A4B[*33] [CRC=DD1ECE0F. hw_OR=31. cnt=16384. blkSize= 128].format
     static constexpr int THREEFRY_ROTATION_32_4[8][2] = {
         {10, 26},
         {11, 21},
         {13, 27},
         {23,  5},
         { 6, 20},
         {17, 11},
         {25, 10},
         {18, 20}
     };
     return THREEFRY_ROTATION_32_4[indexX][indexY];
 }
  
 template<>
 __forceinline__ __device__ __host__ int threefry_rotation_array<unsigned long long>(int indexX,
                                                                                     int indexY)
 {
     // These are the R_256 constants from the Threefish reference sources
     // with names changed to R_64x4... */
     static constexpr int THREEFRY_ROTATION_64_4[8][2] = {
         {14, 16},
         {52, 57},
         {23, 40},
         { 5, 37},
         {25, 33},
         {46, 12},
         {58, 22},
         {32, 32}
     };
     return THREEFRY_ROTATION_64_4[indexX][indexY];
 }
  
 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];
  
         for(unsigned int round_idx = 0; round_idx < Nrounds; round_idx++)
         {
             int rot_0 = threefry_rotation_array<value>(round_idx & 7u, 0);
             int rot_1 = threefry_rotation_array<value>(round_idx & 7u, 1);
             if((round_idx & 2u) == 0)
             {
                 X.x += X.y;
                 X.y = rotl<value>(X.y, rot_0);
                 X.y ^= X.x;
                 X.z += X.w;
                 X.w = rotl<value>(X.w, rot_1);
                 X.w ^= X.z;
             }
             else
             {
                 X.x += X.w;
                 X.w = rotl<value>(X.w, rot_0);
                 X.w ^= X.x;
                 X.z += X.y;
                 X.y = rotl<value>(X.y, rot_1);
                 X.y ^= X.z;
             }
  
             if((round_idx & 3u) == 3)
             {
                 unsigned int inject_idx = round_idx / 4;
                 // InjectKey(r = 1 + inject_idx)
                 X.x += ks[(1 + inject_idx) % 5];
                 X.y += ks[(2 + inject_idx) % 5];
                 X.z += ks[(3 + inject_idx) % 5];
                 X.w += ks[(4 + inject_idx) % 5];
                 X.w += 1 + inject_idx;
             }
         }
  
         return X;
     }
  
     __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_