text: /*
   * This file is part of the GROMACS molecular simulation package.
   *
   * Copyright (c) 2014,2015,2019, by the GROMACS development team, led by
   * Mark Abraham, David van der Spoel, Berk Hess, and Erik Lindahl,
   * and including many others, as listed in the AUTHORS file in the
   * top-level source directory and at http://www.gromacs.org.
   *
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   */
  
  #ifndef GMX_SIMD_IMPL_REFERENCE_SIMD4_DOUBLE_H
  #define GMX_SIMD_IMPL_REFERENCE_SIMD4_DOUBLE_H
  
  /*! \libinternal \file
   *
   * \brief Reference implementation, SIMD4 single precision.
   *
   * \author Erik Lindahl <erik.lindahl@scilifelab.se>
   *
   * \ingroup module_simd
   */
  
  #include "config.h"
  
  #include <cassert>
  #include <cmath>
  #include <cstddef>
  #include <cstdint>
  
  #include <algorithm>
  #include <array>
  
  #include "impl_reference_definitions.h"
  
  namespace gmx
  {
  
  /*! \cond libapi */
  /*! \addtogroup module_simd */
  /*! \{ */
  
  /*! \name Constant width-4 double precision SIMD types and instructions
   * \{
   */
  
  /*! \libinternal \brief SIMD4 double type.
   *
   * Available if \ref GMX_SIMD4_HAVE_DOUBLE is 1.
   *
   * \note This variable cannot be placed inside other structures or classes, since
   *       some compilers (including at least clang-3.7) appear to lose the
   *       alignment. This is likely particularly severe when allocating such
   *       memory on the heap, but it occurs for stack structures too.
   */
  class Simd4Double
  {
  public:
      Simd4Double() {}
  
      //! \brief Construct from scalar
      Simd4Double(double d) { simdInternal_.fill(d); }
  
      /*! \brief Internal SIMD data. Implementation dependent, don't touch.
       *
       * This has to be public to enable usage in combination with static inline
       * functions, but it should never, EVER, be accessed by any code outside
       * the corresponding implementation directory since the type will depend
       * on the architecture.
       */
      std::array<double, GMX_SIMD4_WIDTH> simdInternal_;
  };
  
  /*! \libinternal  \brief SIMD4 variable type to use for logical comparisons on doubles.
   *
   * Available if \ref GMX_SIMD4_HAVE_DOUBLE is 1.
   *
   * \note This variable cannot be placed inside other structures or classes, since
   *       some compilers (including at least clang-3.7) appear to lose the
   *       alignment. This is likely particularly severe when allocating such
   *       memory on the heap, but it occurs for stack structures too.
   */
  class Simd4DBool
  {
  public:
      Simd4DBool() {}
  
      //! \brief Construct from scalar
      Simd4DBool(bool b) { simdInternal_.fill(b); }
  
      /*! \brief Internal SIMD data. Implementation dependent, don't touch.
       *
       * This has to be public to enable usage in combination with static inline
       * functions, but it should never, EVER, be accessed by any code outside
       * the corresponding implementation directory since the type will depend
       * on the architecture.
       */
      std::array<bool, GMX_SIMD4_WIDTH> simdInternal_;
  };
  
  /*! \brief Load 4 double values from aligned memory into SIMD4 variable.
   *
   * \param m Pointer to memory aligned to 4 elements.
   * \return SIMD4 variable with data loaded.
   */
  static inline Simd4Double gmx_simdcall load4(const double* m)
  {
      Simd4Double a;
  
      assert(std::size_t(m) % (a.simdInternal_.size() * sizeof(double)) == 0);
  
      std::copy(m, m + a.simdInternal_.size(), a.simdInternal_.begin());
      return a;
  }
  
  /*! \brief Store the contents of SIMD4 double to aligned memory m.
   *
   * \param[out] m Pointer to memory, aligned to 4 elements.
   * \param a SIMD4 variable to store
   */
  static inline void gmx_simdcall store4(double* m, Simd4Double a)
  {
      assert(std::size_t(m) % (a.simdInternal_.size() * sizeof(double)) == 0);
  
      std::copy(a.simdInternal_.begin(), a.simdInternal_.end(), m);
  }
  
  /*! \brief Load SIMD4 double from unaligned memory.
   *
   * Available if \ref GMX_SIMD_HAVE_LOADU is 1.
   *
   * \param m Pointer to memory, no alignment requirement.
   * \return SIMD4 variable with data loaded.
   */
  static inline Simd4Double gmx_simdcall load4U(const double* m)
  {
      Simd4Double a;
      std::copy(m, m + a.simdInternal_.size(), a.simdInternal_.begin());
      return a;
  }
  
  /*! \brief Store SIMD4 double to unaligned memory.
   *
   * Available if \ref GMX_SIMD_HAVE_STOREU is 1.
   *
   * \param[out] m Pointer to memory, no alignment requirement.
   * \param a SIMD4 variable to store.
   */
  static inline void gmx_simdcall store4U(double* m, Simd4Double a)
  {
      std::copy(a.simdInternal_.begin(), a.simdInternal_.end(), m);
  }
  
  /*! \brief Set all SIMD4 double elements to 0.
   *
   * You should typically just call \ref gmx::setZero(), which uses proxy objects
   * internally to handle all types rather than adding the suffix used here.
   *
   * \return SIMD4 0.0
   */
  static inline Simd4Double gmx_simdcall simd4SetZeroD()
  {
      return Simd4Double(0.0);
  }
  
  
  /*! \brief Bitwise and for two SIMD4 double variables.
   *
   * Supported if \ref GMX_SIMD_HAVE_LOGICAL is 1.
   *
   * \param a data1
   * \param b data2
   * \return data1 & data2
   */
  static inline Simd4Double gmx_simdcall operator&(Simd4Double a, Simd4Double b)
  {
      Simd4Double res;
  
      union {
          double       r;
          std::int64_t i;
      } conv1, conv2;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          conv1.r              = a.simdInternal_[i];
          conv2.r              = b.simdInternal_[i];
          conv1.i              = conv1.i & conv2.i;
          res.simdInternal_[i] = conv1.r;
      }
      return res;
  }
  
  
  /*! \brief Bitwise andnot for two SIMD4 double variables. c=(~a) & b.
   *
   * Available if \ref GMX_SIMD_HAVE_LOGICAL is 1.
   *
   * \param a data1
   * \param b data2
   * \return (~data1) & data2
   */
  static inline Simd4Double gmx_simdcall andNot(Simd4Double a, Simd4Double b)
  {
      Simd4Double res;
  
      union {
          double       r;
          std::int64_t i;
      } conv1, conv2;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          conv1.r              = a.simdInternal_[i];
          conv2.r              = b.simdInternal_[i];
          conv1.i              = ~conv1.i & conv2.i;
          res.simdInternal_[i] = conv1.r;
      }
      return res;
  }
  
  
  /*! \brief Bitwise or for two SIMD4 doubles.
   *
   * Available if \ref GMX_SIMD_HAVE_LOGICAL is 1.
   *
   * \param a data1
   * \param b data2
   * \return data1 | data2
   */
  static inline Simd4Double gmx_simdcall operator|(Simd4Double a, Simd4Double b)
  {
      Simd4Double res;
  
      union {
          double       r;
          std::int64_t i;
      } conv1, conv2;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          conv1.r              = a.simdInternal_[i];
          conv2.r              = b.simdInternal_[i];
          conv1.i              = conv1.i | conv2.i;
          res.simdInternal_[i] = conv1.r;
      }
      return res;
  }
  
  /*! \brief Bitwise xor for two SIMD4 double variables.
   *
   * Available if \ref GMX_SIMD_HAVE_LOGICAL is 1.
   *
   * \param a data1
   * \param b data2
   * \return data1 ^ data2
   */
  static inline Simd4Double gmx_simdcall operator^(Simd4Double a, Simd4Double b)
  {
      Simd4Double res;
  
      union {
          double       r;
          std::int64_t i;
      } conv1, conv2;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          conv1.r              = a.simdInternal_[i];
          conv2.r              = b.simdInternal_[i];
          conv1.i              = conv1.i ^ conv2.i;
          res.simdInternal_[i] = conv1.r;
      }
      return res;
  }
  
  /*! \brief Add two double SIMD4 variables.
   *
   * \param a term1
   * \param b term2
   * \return a+b
   */
  static inline Simd4Double gmx_simdcall operator+(Simd4Double a, Simd4Double b)
  {
      Simd4Double res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = a.simdInternal_[i] + b.simdInternal_[i];
      }
      return res;
  }
  
  /*! \brief Subtract two SIMD4 variables.
   *
   * \param a term1
   * \param b term2
   * \return a-b
   */
  static inline Simd4Double gmx_simdcall operator-(Simd4Double a, Simd4Double b)
  {
      Simd4Double res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = a.simdInternal_[i] - b.simdInternal_[i];
      }
      return res;
  }
  
  /*! \brief SIMD4 floating-point negate.
   *
   * \param a SIMD4 floating-point value
   * \return -a
   */
  static inline Simd4Double gmx_simdcall operator-(Simd4Double a)
  {
      Simd4Double res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = -a.simdInternal_[i];
      }
      return res;
  }
  
  /*! \brief Multiply two SIMD4 variables.
   *
   * \param a factor1
   * \param b factor2
   * \return a*b.
   */
  static inline Simd4Double gmx_simdcall operator*(Simd4Double a, Simd4Double b)
  {
      Simd4Double res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = a.simdInternal_[i] * b.simdInternal_[i];
      }
      return res;
  }
  
  /*! \brief SIMD4 Fused-multiply-add. Result is a*b+c.
   *
   * \param a factor1
   * \param b factor2
   * \param c term
   * \return a*b+c
   */
  static inline Simd4Double gmx_simdcall fma(Simd4Double a, Simd4Double b, Simd4Double c)
  {
      return a * b + c;
  }
  
  /*! \brief SIMD4 Fused-multiply-subtract. Result is a*b-c.
   *
   * \param a factor1
   * \param b factor2
   * \param c term
   * \return a*b-c
   */
  static inline Simd4Double gmx_simdcall fms(Simd4Double a, Simd4Double b, Simd4Double c)
  {
      return a * b - c;
  }
  
  /*! \brief SIMD4 Fused-negated-multiply-add. Result is -a*b+c.
   *
   * \param a factor1
   * \param b factor2
   * \param c term
   * \return -a*b+c
   */
  static inline Simd4Double gmx_simdcall fnma(Simd4Double a, Simd4Double b, Simd4Double c)
  {
      return c - a * b;
  }
  
  /*! \brief SIMD4 Fused-negated-multiply-subtract. Result is -a*b-c.
   *
   * \param a factor1
   * \param b factor2
   * \param c term
   * \return -a*b-c
   */
  static inline Simd4Double gmx_simdcall fnms(Simd4Double a, Simd4Double b, Simd4Double c)
  {
      return -a * b - c;
  }
  
  /*! \brief SIMD4 1.0/sqrt(x) lookup.
   *
   * This is a low-level instruction that should only be called from routines
   * implementing the inverse square root in simd_math.h.
   *
   * \param x Argument, x>0
   * \return Approximation of 1/sqrt(x), accuracy is \ref GMX_SIMD_RSQRT_BITS.
   */
  static inline Simd4Double gmx_simdcall rsqrt(Simd4Double x)
  {
      Simd4Double res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          // sic - we only use single precision for the lookup
          res.simdInternal_[i] = 1.0F / std::sqrt(static_cast<float>(x.simdInternal_[i]));
      }
      return res;
  };
  
  
  /*! \brief SIMD4 Floating-point abs().
   *
   * \param a any floating point values
   * \return fabs(a) for each element.
   */
  static inline Simd4Double gmx_simdcall abs(Simd4Double a)
  {
      Simd4Double res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = std::abs(a.simdInternal_[i]);
      }
      return res;
  }
  
  /*! \brief Set each SIMD4 element to the largest from two variables.
   *
   * \param a Any floating-point value
   * \param b Any floating-point value
   * \return max(a,b) for each element.
   */
  static inline Simd4Double gmx_simdcall max(Simd4Double a, Simd4Double b)
  {
      Simd4Double res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = std::max(a.simdInternal_[i], b.simdInternal_[i]);
      }
      return res;
  }
  
  
  /*! \brief Set each SIMD4 element to the largest from two variables.
   *
   * \param a Any floating-point value
   * \param b Any floating-point value
   * \return max(a,b) for each element.
   */
  static inline Simd4Double gmx_simdcall min(Simd4Double a, Simd4Double b)
  {
      Simd4Double res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = std::min(a.simdInternal_[i], b.simdInternal_[i]);
      }
      return res;
  }
  
  
  /*! \brief SIMD4 Round to nearest integer value (in floating-point format).
   *
   * \param a Any floating-point value
   * \return The nearest integer, represented in floating-point format.
   */
  static inline Simd4Double gmx_simdcall round(Simd4Double a)
  {
      Simd4Double res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = std::round(a.simdInternal_[i]);
      }
      return res;
  }
  
  
  /*! \brief Truncate SIMD4, i.e. round towards zero - common hardware instruction.
   *
   * \param a Any floating-point value
   * \return Integer rounded towards zero, represented in floating-point format.
   *
   * \note This is truncation towards zero, not floor(). The reason for this
   * is that truncation is virtually always present as a dedicated hardware
   * instruction, but floor() frequently isn't.
   */
  static inline Simd4Double gmx_simdcall trunc(Simd4Double a)
  {
      Simd4Double res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = std::trunc(a.simdInternal_[i]);
      }
      return res;
  }
  
  /*! \brief Return dot product of two double precision SIMD4 variables.
   *
   * The dot product is calculated between the first three elements in the two
   * vectors, while the fourth is ignored. The result is returned as a scalar.
   *
   * \param a vector1
   * \param b vector2
   * \result a[0]*b[0]+a[1]*b[1]+a[2]*b[2], returned as scalar. Last element is ignored.
   */
  static inline double gmx_simdcall dotProduct(Simd4Double a, Simd4Double b)
  {
      return (a.simdInternal_[0] * b.simdInternal_[0] + a.simdInternal_[1] * b.simdInternal_[1]
              + a.simdInternal_[2] * b.simdInternal_[2]);
  }
  
  /*! \brief SIMD4 double transpose
   *
   * \param[in,out] v0  Row 0 on input, column 0 on output
   * \param[in,out] v1  Row 1 on input, column 1 on output
   * \param[in,out] v2  Row 2 on input, column 2 on output
   * \param[in,out] v3  Row 3 on input, column 3 on output
   */
  static inline void gmx_simdcall transpose(Simd4Double* v0, Simd4Double* v1, Simd4Double* v2, Simd4Double* v3)
  {
      Simd4Double t0       = *v0;
      Simd4Double t1       = *v1;
      Simd4Double t2       = *v2;
      Simd4Double t3       = *v3;
      v0->simdInternal_[0] = t0.simdInternal_[0];
      v0->simdInternal_[1] = t1.simdInternal_[0];
      v0->simdInternal_[2] = t2.simdInternal_[0];
      v0->simdInternal_[3] = t3.simdInternal_[0];
      v1->simdInternal_[0] = t0.simdInternal_[1];
      v1->simdInternal_[1] = t1.simdInternal_[1];
      v1->simdInternal_[2] = t2.simdInternal_[1];
      v1->simdInternal_[3] = t3.simdInternal_[1];
      v2->simdInternal_[0] = t0.simdInternal_[2];
      v2->simdInternal_[1] = t1.simdInternal_[2];
      v2->simdInternal_[2] = t2.simdInternal_[2];
      v2->simdInternal_[3] = t3.simdInternal_[2];
      v3->simdInternal_[0] = t0.simdInternal_[3];
      v3->simdInternal_[1] = t1.simdInternal_[3];
      v3->simdInternal_[2] = t2.simdInternal_[3];
      v3->simdInternal_[3] = t3.simdInternal_[3];
  }
  
  /*! \brief a==b for SIMD4 double
   *
   * \param a value1
   * \param b value2
   * \return Each element of the boolean will be set to true if a==b.
   */
  static inline Simd4DBool gmx_simdcall operator==(Simd4Double a, Simd4Double b)
  {
      Simd4DBool res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = (a.simdInternal_[i] == b.simdInternal_[i]);
      }
      return res;
  }
  
  /*! \brief a!=b for SIMD4 double
   *
   * \param a value1
   * \param b value2
   * \return Each element of the boolean will be set to true if a!=b.
   */
  static inline Simd4DBool gmx_simdcall operator!=(Simd4Double a, Simd4Double b)
  {
      Simd4DBool res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = (a.simdInternal_[i] != b.simdInternal_[i]);
      }
      return res;
  }
  
  /*! \brief a<b for SIMD4 double
   *
   * \param a value1
   * \param b value2
   * \return Each element of the boolean will be set to true if a<b.
   */
  static inline Simd4DBool gmx_simdcall operator<(Simd4Double a, Simd4Double b)
  {
      Simd4DBool res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = (a.simdInternal_[i] < b.simdInternal_[i]);
      }
      return res;
  }
  
  
  /*! \brief a<=b for SIMD4 double.
   *
   * \param a value1
   * \param b value2
   * \return Each element of the boolean will be set to true if a<=b.
   */
  static inline Simd4DBool gmx_simdcall operator<=(Simd4Double a, Simd4Double b)
  {
      Simd4DBool res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = (a.simdInternal_[i] <= b.simdInternal_[i]);
      }
      return res;
  }
  
  /*! \brief Logical \a and on single precision SIMD4 booleans.
   *
   * \param a logical vars 1
   * \param b logical vars 2
   * \return For each element, the result boolean is true if a \& b are true.
   *
   * \note This is not necessarily a bitwise operation - the storage format
   * of booleans is implementation-dependent.
   */
  static inline Simd4DBool gmx_simdcall operator&&(Simd4DBool a, Simd4DBool b)
  {
      Simd4DBool res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = (a.simdInternal_[i] && b.simdInternal_[i]);
      }
      return res;
  }
  
  /*! \brief Logical \a or on single precision SIMD4 booleans.
   *
   * \param a logical vars 1
   * \param b logical vars 2
   * \return For each element, the result boolean is true if a or b is true.
   *
   * Note that this is not necessarily a bitwise operation - the storage format
   * of booleans is implementation-dependent.
   */
  static inline Simd4DBool gmx_simdcall operator||(Simd4DBool a, Simd4DBool b)
  {
      Simd4DBool res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = (a.simdInternal_[i] || b.simdInternal_[i]);
      }
      return res;
  }
  
  /*! \brief Returns non-zero if any of the boolean in SIMD4 a is True, otherwise 0.
   *
   * \param a Logical variable.
   * \return true if any element in a is true, otherwise false.
   *
   * The actual return value for truth will depend on the architecture,
   * so any non-zero value is considered truth.
   */
  static inline bool gmx_simdcall anyTrue(Simd4DBool a)
  {
      bool res = false;
  
      for (std::size_t i = 0; i < a.simdInternal_.size(); i++)
      {
          res = res || a.simdInternal_[i];
      }
      return res;
  }
  
  /*! \brief Select from single precision SIMD4 variable where boolean is true.
   *
   * \param a Floating-point variable to select from
   * \param mask Boolean selector
   * \return  For each element, a is selected for true, 0 for false.
   */
  static inline Simd4Double gmx_simdcall selectByMask(Simd4Double a, Simd4DBool mask)
  {
      Simd4Double res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = mask.simdInternal_[i] ? a.simdInternal_[i] : 0.0;
      }
      return res;
  }
  
  /*! \brief Select from single precision SIMD4 variable where boolean is false.
   *
   * \param a Floating-point variable to select from
   * \param mask Boolean selector
   * \return  For each element, a is selected for false, 0 for true (sic).
   */
  static inline Simd4Double gmx_simdcall selectByNotMask(Simd4Double a, Simd4DBool mask)
  {
      Simd4Double res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = mask.simdInternal_[i] ? 0.0 : a.simdInternal_[i];
      }
      return res;
  }
  
  
  /*! \brief Vector-blend SIMD4 selection.
   *
   * \param a First source
   * \param b Second source
   * \param sel Boolean selector
   * \return For each element, select b if sel is true, a otherwise.
   */
  static inline Simd4Double gmx_simdcall blend(Simd4Double a, Simd4Double b, Simd4DBool sel)
  {
      Simd4Double res;
  
      for (std::size_t i = 0; i < res.simdInternal_.size(); i++)
      {
          res.simdInternal_[i] = sel.simdInternal_[i] ? b.simdInternal_[i] : a.simdInternal_[i];
      }
      return res;
  }
  
  
  /*! \brief Return sum of all elements in SIMD4 double variable.
   *
   * \param a SIMD4 variable to reduce/sum.
   * \return The sum of all elements in the argument variable.
   *
   */
  static inline double gmx_simdcall reduce(Simd4Double a)
  {
      double sum = 0.0;
  
      for (std::size_t i = 0; i < a.simdInternal_.size(); i++)
      {
          sum += a.simdInternal_[i];
      }
      return sum;
  }
  
  //! \}
  
  //! \}
  
  //! \endcond
  
  } // namespace gmx
  
  #endif // GMX_SIMD_IMPL_REFERENCE_SIMD4_DOUBLE_H
  