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API library: /home/docs/checkouts/readthedocs.org/user_builds/advanced-micro-devices-rocrand/checkouts/docs-6.2.0/library/include/rocrand/rocrand_threefry2_impl.h Source File
API library
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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.
  
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   contributors may be used to endorse or promote products derived from
   this software without specific prior written permission.
  
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 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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 */
  
 #ifndef ROCRAND_THREEFRY2_IMPL_H_
 #define ROCRAND_THREEFRY2_IMPL_H_
  
 #include "rocrand/rocrand_threefry_common.h"
 #include <rocrand/rocrand_common.h>
  
 #ifndef THREEFRY2x32_DEFAULT_ROUNDS
     #define THREEFRY2x32_DEFAULT_ROUNDS 20
 #endif
  
 #ifndef THREEFRY2x64_DEFAULT_ROUNDS
     #define THREEFRY2x64_DEFAULT_ROUNDS 20
 #endif
  
 namespace rocrand_device
 {
  
 template<class value>
 __forceinline__ __device__ __host__ int threefry_rotation_array(int index) = delete;
  
 template<>
 __forceinline__ __device__ __host__ int threefry_rotation_array<unsigned int>(int index)
 {
     // Output from skein_rot_search (srs32x2-X5000.out)
     // Random seed = 1. BlockSize = 64 bits. sampleCnt =  1024. rounds =  8, minHW_or=28
     // Start: Tue Jul 12 11:11:33 2011
     // rMin = 0.334. #0206[*07] [CRC=1D9765C0. hw_OR=32. cnt=16384. blkSize=  64].format
     static constexpr int THREEFRY_ROTATION_32_2[8] = {13, 15, 26, 6, 17, 29, 16, 24};
     return THREEFRY_ROTATION_32_2[index];
 }
  
 template<>
 __forceinline__ __device__ __host__ int threefry_rotation_array<unsigned long long>(int index)
 {
     // Output from skein_rot_search: (srs64_B64-X1000)
     // Random seed = 1. BlockSize = 128 bits. sampleCnt =  1024. rounds =  8, minHW_or=57
     // Start: Tue Mar  1 10:07:48 2011
     // rMin = 0.136. #0325[*15] [CRC=455A682F. hw_OR=64. cnt=16384. blkSize= 128].format
     static constexpr int THREEFRY_ROTATION_64_2[8] = {16, 42, 12, 31, 16, 32, 24, 21};
     return THREEFRY_ROTATION_64_2[index];
 }
  
 template<typename state_value, typename value, unsigned int Nrounds>
 class threefry_engine2_base
 {
 public:
     struct threefry_state_2
     {
         state_value  counter;
         state_value  key;
         state_value  result;
         unsigned int substate;
     };
     using state_type        = threefry_state_2;
     using state_vector_type = state_value;
  
     __forceinline__ __device__ __host__ void discard(unsigned long long offset)
     {
         this->discard_impl(offset);
         m_state.result = this->threefry_rounds(m_state.counter, m_state.key);
     }
  
     __forceinline__ __device__ __host__ void discard()
     {
         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 = m_state.result.data[m_state.substate];
 #else
         value ret = (&m_state.result.x)[m_state.substate];
 #endif
         m_state.substate++;
         if(m_state.substate == 2)
         {
             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 next2()
     {
         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[2 + 1];
  
         static_assert(Nrounds <= 32, "32 or less only supported in threefry rounds");
  
         ks[2] = skein_ks_parity<value>();
  
         ks[0] = key.x;
         ks[1] = key.y;
  
         X.x = counter.x;
         X.y = counter.y;
  
         ks[2] ^= key.x;
         ks[2] ^= key.y;
  
         /* Insert initial key before round 0 */
         X.x += ks[0];
         X.y += ks[1];
  
         for(unsigned int round_idx = 0; round_idx < Nrounds; round_idx++)
         {
             X.x += X.y;
             X.y = rotl<value>(X.y, threefry_rotation_array<value>(round_idx & 7u));
             X.y ^= X.x;
  
             if((round_idx & 3u) == 3)
             {
                 unsigned int inject_idx = round_idx / 4;
                 // InjectKey(r = 1 + inject_idx)
                 X.x += ks[(1 + inject_idx) % 3];
                 X.y += ks[(2 + inject_idx) % 3];
                 X.y += 1 + inject_idx;
             }
         }
  
         return X;
     }
  
     __forceinline__ __device__ __host__ void discard_impl(unsigned long long offset)
     {
         // Adjust offset for subset
         m_state.substate += offset & 1;
         unsigned long long counter_offset = offset / 2;
         counter_offset += m_state.substate < 2 ? 0 : 1;
         m_state.substate += m_state.substate < 2 ? 0 : -2;
         // Discard states
         this->discard_state(counter_offset);
     }
  
     __forceinline__ __device__ __host__ void
         discard_subsequence_impl(unsigned long long subsequence)
     {
         m_state.counter.y += subsequence;
     }
  
     __forceinline__ __device__ __host__ void discard_state(unsigned long long offset)
     {
         value lo, hi;
         ::rocrand_device::detail::split_ull(lo, hi, offset);
  
         value old_counter = m_state.counter.x;
         m_state.counter.x += lo;
         m_state.counter.y += hi + (m_state.counter.x < old_counter ? 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;
         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, next.x};
         }
         __builtin_unreachable();
     }
  
 protected:
     threefry_state_2 m_state;
 }; // threefry_engine2_base class
  
 } // end namespace rocrand_device
  
 #endif // ROCRAND_THREEFRY2_IMPL_H_