Evaluation.hpp

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// -*- mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
// vi: set et ts=4 sw=4 sts=4:
/*
  This file is part of the Open Porous Media project (OPM).

  OPM is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 2 of the License, or
  (at your option) any later version.

  OPM is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with OPM.  If not, see <http://www.gnu.org/licenses/>.

  Consult the COPYING file in the top-level source directory of this
  module for the precise wording of the license and the list of
  copyright holders.
*/
#ifndef OPM_DENSEAD_EVALUATION_HPP
#define OPM_DENSEAD_EVALUATION_HPP

#ifndef NDEBUG
#include <opm/material/common/Valgrind.hpp>
#endif

#include <array>
#include <cassert>
#include <iosfwd>
#include <stdexcept>

#include <opm/common/ErrorMacros.hpp>
#include <opm/common/utility/gpuDecorators.hpp>

#if HAVE_DUNE_COMMON
#include <dune/common/typetraits.hh>
#endif

namespace Opm {
namespace DenseAd {

static constexpr int DynamicSize = -1;

template <class ValueT, int numDerivs, unsigned staticSize = 0>
class Evaluation
{
public:
    static const int numVars = numDerivs;

    typedef ValueT ValueType;

    OPM_HOST_DEVICE constexpr int size() const
    { return numDerivs; }

protected:
    OPM_HOST_DEVICE constexpr int length_() const
    { return size() + 1; }


    OPM_HOST_DEVICE constexpr int valuepos_() const
    { return 0; }
    OPM_HOST_DEVICE constexpr int dstart_() const
    { return 1; }
    OPM_HOST_DEVICE constexpr int dend_() const
    { return length_(); }

    OPM_HOST_DEVICE constexpr void checkDefined_() const
    {
#ifndef NDEBUG
       for (const auto& v: data_)
           Valgrind::CheckDefined(v);
#endif
    }

public:
    OPM_HOST_DEVICE Evaluation() : data_()
    {}

    Evaluation(const Evaluation& other) = default;


    // create an evaluation which represents a constant function
    //
    // i.e., f(x) = c. this implies an evaluation with the given value and all
    // derivatives being zero.
    template <class RhsValueType>
    OPM_HOST_DEVICE constexpr Evaluation(const RhsValueType& c): data_{}
    {
        setValue(c);
        clearDerivatives();

        //checkDefined_();
    }

    // create an evaluation representing a variable with the variable position of varPos
    // The value is set to c, all derivatives are zero except for the one at varPos, which is set to 1.
    template <class RhsValueType>
    OPM_HOST_DEVICE Evaluation(const RhsValueType& c, int varPos)
    {
        // The variable position must be in represented by the given variable descriptor
        assert(0 <= varPos && varPos < size());

        setValue( c );
        clearDerivatives();

        data_[varPos + dstart_()] = 1.0;

        checkDefined_();
    }

    // set all derivatives to zero
    OPM_HOST_DEVICE constexpr void clearDerivatives()
    {
        for (int i = dstart_(); i < dend_(); ++i)
            data_[i] = 0.0;
    }

    // create an uninitialized Evaluation object that is compatible with the
    // argument, but not initialized
    //
    // This basically boils down to the copy constructor without copying
    // anything. If the number of derivatives is known at compile time, this
    // is equivalent to creating an uninitialized object using the default
    // constructor, while for dynamic evaluations, it creates an Evaluation
    // object which exhibits the same number of derivatives as the argument.
    OPM_HOST_DEVICE static Evaluation createBlank(const Evaluation&)
    { return Evaluation(); }

    // create an Evaluation with value and all the derivatives to be zero
    OPM_HOST_DEVICE static Evaluation createConstantZero(const Evaluation&)
    { return Evaluation(0.); }

    // create an Evaluation with value to be one and all the derivatives to be zero
    OPM_HOST_DEVICE static Evaluation createConstantOne(const Evaluation&)
    { return Evaluation(1.); }

    // create a function evaluation for a "naked" depending variable (i.e., f(x) = x)
    template <class RhsValueType>
    OPM_HOST_DEVICE static Evaluation createVariable(const RhsValueType& value, int varPos)
    {
        // copy function value and set all derivatives to 0, except for the variable
        // which is represented by the value (which is set to 1.0)
        return Evaluation(value, varPos);
    }

    template <class RhsValueType>
    OPM_HOST_DEVICE static Evaluation createVariable(int nVars, const RhsValueType& value, int varPos)
    {
        if (nVars != 0)
            throw std::logic_error("This statically-sized evaluation can only represent objects"
                                   " with 0 derivatives");

        // copy function value and set all derivatives to 0, except for the variable
        // which is represented by the value (which is set to 1.0)
        return Evaluation(nVars, value, varPos);
    }

    template <class RhsValueType>
    OPM_HOST_DEVICE static Evaluation createVariable(const Evaluation&, const RhsValueType& value, int varPos)
    {
        // copy function value and set all derivatives to 0, except for the variable
        // which is represented by the value (which is set to 1.0)
        return Evaluation(value, varPos);
    }


    // "evaluate" a constant function (i.e. a function that does not depend on the set of
    // relevant variables, f(x) = c).
    template <class RhsValueType>
    OPM_HOST_DEVICE static Evaluation createConstant(int nVars, const RhsValueType& value)
    {
        if (nVars != 0)
            throw std::logic_error("This statically-sized evaluation can only represent objects"
                                   " with 0 derivatives");
        return Evaluation(value);
    }

    // "evaluate" a constant function (i.e. a function that does not depend on the set of
    // relevant variables, f(x) = c).
    template <class RhsValueType>
    OPM_HOST_DEVICE static Evaluation createConstant(const RhsValueType& value)
    {
        return Evaluation(value);
    }

    // "evaluate" a constant function (i.e. a function that does not depend on the set of
    // relevant variables, f(x) = c).
    template <class RhsValueType>
    OPM_HOST_DEVICE static Evaluation createConstant(const Evaluation&, const RhsValueType& value)
    {
        return Evaluation(value);
    }

    // copy all derivatives from other
    OPM_HOST_DEVICE void copyDerivatives(const Evaluation& other)
    {
        assert(size() == other.size());

        for (int i = dstart_(); i < dend_(); ++i)
            data_[i] = other.data_[i];
    }


    // add value and derivatives from other to this value and derivatives
    OPM_HOST_DEVICE Evaluation& operator+=(const Evaluation& other)
    {
        assert(size() == other.size());

        for (int i = 0; i < length_(); ++i)
            data_[i] += other.data_[i];

        return *this;
    }

    // add value from other to this values
    template <class RhsValueType>
    OPM_HOST_DEVICE Evaluation& operator+=(const RhsValueType& other)
    {
        // value is added, derivatives stay the same
        data_[valuepos_()] += other;

        return *this;
    }

    // subtract other's value and derivatives from this values
    OPM_HOST_DEVICE Evaluation& operator-=(const Evaluation& other)
    {
        assert(size() == other.size());

        for (int i = 0; i < length_(); ++i)
            data_[i] -= other.data_[i];

        return *this;
    }

    // subtract other's value from this values
    template <class RhsValueType>
    OPM_HOST_DEVICE Evaluation& operator-=(const RhsValueType& other)
    {
        // for constants, values are subtracted, derivatives stay the same
        data_[valuepos_()] -= other;

        return *this;
    }

    // multiply values and apply chain rule to derivatives: (u*v)' = (v'u + u'v)
    OPM_HOST_DEVICE Evaluation& operator*=(const Evaluation& other)
    {
        assert(size() == other.size());

        // while the values are multiplied, the derivatives follow the product rule,
        // i.e., (u*v)' = (v'u + u'v).
        const ValueType u = this->value();
        const ValueType v = other.value();

        // value
        data_[valuepos_()] *= v ;

        //  derivatives
        for (int i = dstart_(); i < dend_(); ++i)
            data_[i] = data_[i] * v + other.data_[i] * u;

        return *this;
    }

    // m(c*u)' = c*u'
    template <class RhsValueType>
    OPM_HOST_DEVICE Evaluation& operator*=(const RhsValueType& other)
    {
        for (int i = 0; i < length_(); ++i)
            data_[i] *= other;

        return *this;
    }

    // m(u*v)' = (vu' - uv')/v^2
    OPM_HOST_DEVICE Evaluation& operator/=(const Evaluation& other)
    {
        assert(size() == other.size());

        // values are divided, derivatives follow the rule for division, i.e., (u/v)' = (v'u -
        // u'v)/v^2.
        ValueType& u = data_[valuepos_()];
        const ValueType& v = other.value();
        for (int idx = dstart_(); idx < dend_(); ++idx) {
            const ValueType& uPrime = data_[idx];
            const ValueType& vPrime = other.data_[idx];

            data_[idx] = (v*uPrime - u*vPrime)/(v*v);
        }
        u /= v;

        return *this;
    }

    // divide value and derivatives by value of other
    template <class RhsValueType>
    OPM_HOST_DEVICE Evaluation& operator/=(const RhsValueType& other)
    {
        const ValueType tmp = 1.0/other;

        for (int i = 0; i < length_(); ++i)
            data_[i] *= tmp;

        return *this;
    }

    // add two evaluation objects
    OPM_HOST_DEVICE Evaluation operator+(const Evaluation& other) const
    {
        assert(size() == other.size());

        Evaluation result(*this);

        result += other;

        return result;
    }

    // add constant to this object
    template <class RhsValueType>
    OPM_HOST_DEVICE Evaluation operator+(const RhsValueType& other) const
    {
        Evaluation result(*this);

        result += other;

        return result;
    }

    // subtract two evaluation objects
    OPM_HOST_DEVICE Evaluation operator-(const Evaluation& other) const
    {
        assert(size() == other.size());

        Evaluation result(*this);

        result -= other;

        return result;
    }

    // subtract constant from evaluation object
    template <class RhsValueType>
    OPM_HOST_DEVICE Evaluation operator-(const RhsValueType& other) const
    {
        Evaluation result(*this);

        result -= other;

        return result;
    }

    // negation (unary minus) operator
    OPM_HOST_DEVICE Evaluation operator-() const
    {
        Evaluation result;

        // set value and derivatives to negative
        for (int i = 0; i < length_(); ++i)
            result.data_[i] = - data_[i];

        return result;
    }

    OPM_HOST_DEVICE Evaluation operator*(const Evaluation& other) const
    {
        assert(size() == other.size());

        Evaluation result(*this);

        result *= other;

        return result;
    }

    template <class RhsValueType>
    OPM_HOST_DEVICE Evaluation operator*(const RhsValueType& other) const
    {
        Evaluation result(*this);

        result *= other;

        return result;
    }

    OPM_HOST_DEVICE Evaluation operator/(const Evaluation& other) const
    {
        assert(size() == other.size());

        Evaluation result(*this);

        result /= other;

        return result;
    }

    template <class RhsValueType>
    OPM_HOST_DEVICE Evaluation operator/(const RhsValueType& other) const
    {
        Evaluation result(*this);

        result /= other;

        return result;
    }

    template <class RhsValueType>
    OPM_HOST_DEVICE Evaluation& operator=(const RhsValueType& other)
    {
        setValue( other );
        clearDerivatives();

        return *this;
    }

    // copy assignment from evaluation
    Evaluation& operator=(const Evaluation& other) = default;

    template <class RhsValueType>
    OPM_HOST_DEVICE bool operator==(const RhsValueType& other) const
    { return value() == other; }

    OPM_HOST_DEVICE bool operator==(const Evaluation& other) const
    {
        assert(size() == other.size());

        for (int idx = 0; idx < length_(); ++idx) {
            if (data_[idx] != other.data_[idx]) {
                return false;
            }
        }
        return true;
    }

    OPM_HOST_DEVICE bool operator!=(const Evaluation& other) const
    { return !operator==(other); }

    template <class RhsValueType>
    OPM_HOST_DEVICE bool operator!=(const RhsValueType& other) const
    { return !operator==(other); }

    template <class RhsValueType>
    OPM_HOST_DEVICE bool operator>(RhsValueType other) const
    { return value() > other; }

    OPM_HOST_DEVICE bool operator>(const Evaluation& other) const
    {
        assert(size() == other.size());

        return value() > other.value();
    }

    template <class RhsValueType>
    OPM_HOST_DEVICE bool operator<(RhsValueType other) const
    { return value() < other; }

    OPM_HOST_DEVICE bool operator<(const Evaluation& other) const
    {
        assert(size() == other.size());

        return value() < other.value();
    }

    template <class RhsValueType>
    OPM_HOST_DEVICE bool operator>=(RhsValueType other) const
    { return value() >= other; }

    OPM_HOST_DEVICE bool operator>=(const Evaluation& other) const
    {
        assert(size() == other.size());

        return value() >= other.value();
    }

    template <class RhsValueType>
    OPM_HOST_DEVICE bool operator<=(RhsValueType other) const
    { return value() <= other; }

    OPM_HOST_DEVICE bool operator<=(const Evaluation& other) const
    {
        assert(size() == other.size());

        return value() <= other.value();
    }

    // return value of variable
    OPM_HOST_DEVICE const ValueType& value() const
    { return data_[valuepos_()]; }

    // set value of variable
    template <class RhsValueType>
    OPM_HOST_DEVICE constexpr void setValue(const RhsValueType& val)
    { data_[valuepos_()] = val; }

    // return varIdx'th derivative
    OPM_HOST_DEVICE const ValueType& derivative(int varIdx) const
    {
        assert(0 <= varIdx && varIdx < size());

        return data_[dstart_() + varIdx];
    }

    // set derivative at position varIdx
    OPM_HOST_DEVICE void setDerivative(int varIdx, const ValueType& derVal)
    {
        assert(0 <= varIdx && varIdx < size());

        data_[dstart_() + varIdx] = derVal;
    }

    template<class Serializer>
    OPM_HOST_DEVICE void serializeOp(Serializer& serializer)
    {
        serializer(data_);
    }

private:
    std::array<ValueT, numDerivs + 1> data_;
};

// the generic operators are only required for the unspecialized case
template <class RhsValueType, class ValueType, int numVars, unsigned staticSize>
OPM_HOST_DEVICE bool operator<(const RhsValueType& a, const Evaluation<ValueType, numVars, staticSize>& b)
{ return b > a; }

template <class RhsValueType, class ValueType, int numVars, unsigned staticSize>
OPM_HOST_DEVICE bool operator>(const RhsValueType& a, const Evaluation<ValueType, numVars, staticSize>& b)
{ return b < a; }

template <class RhsValueType, class ValueType, int numVars, unsigned staticSize>
OPM_HOST_DEVICE bool operator<=(const RhsValueType& a, const Evaluation<ValueType, numVars, staticSize>& b)
{ return b >= a; }

template <class RhsValueType, class ValueType, int numVars, unsigned staticSize>
OPM_HOST_DEVICE bool operator>=(const RhsValueType& a, const Evaluation<ValueType, numVars, staticSize>& b)
{ return b <= a; }

template <class RhsValueType, class ValueType, int numVars, unsigned staticSize>
OPM_HOST_DEVICE bool operator!=(const RhsValueType& a, const Evaluation<ValueType, numVars, staticSize>& b)
{ return a != b.value(); }

template <class RhsValueType, class ValueType, int numVars, unsigned staticSize>
OPM_HOST_DEVICE Evaluation<ValueType, numVars, staticSize> operator+(const RhsValueType& a, const Evaluation<ValueType, numVars, staticSize>& b)
{
    Evaluation<ValueType, numVars, staticSize> result(b);
    result += a;
    return result;
}

template <class RhsValueType, class ValueType, int numVars, unsigned staticSize>
OPM_HOST_DEVICE Evaluation<ValueType, numVars, staticSize> operator-(const RhsValueType& a, const Evaluation<ValueType, numVars, staticSize>& b)
{
    return -(b - a);
}

template <class RhsValueType, class ValueType, int numVars, unsigned staticSize>
OPM_HOST_DEVICE Evaluation<ValueType, numVars, staticSize> operator/(const RhsValueType& a, const Evaluation<ValueType, numVars, staticSize>& b)
{
    Evaluation<ValueType, numVars, staticSize> tmp(a);
    tmp /= b;
    return tmp;
}

template <class RhsValueType, class ValueType, int numVars, unsigned staticSize>
OPM_HOST_DEVICE Evaluation<ValueType, numVars, staticSize> operator*(const RhsValueType& a, const Evaluation<ValueType, numVars, staticSize>& b)
{
    Evaluation<ValueType, numVars, staticSize> result(b);
    result *= a;
    return result;
}

template<class T>
struct is_evaluation
{
    static constexpr bool value = false;
};

template <class ValueType, int numVars, unsigned staticSize>
struct is_evaluation<Evaluation<ValueType,numVars,staticSize>>
{
    static constexpr bool value = true;
};

template <class ValueType, int numVars, unsigned staticSize>
OPM_HOST_DEVICE void printEvaluation(std::ostream& os,
                     const Evaluation<ValueType, numVars, staticSize>& eval,
                     bool withDer = false);

template <class ValueType, int numVars, unsigned staticSize>
OPM_HOST_DEVICE std::ostream& operator<<(std::ostream& os, const Evaluation<ValueType, numVars, staticSize>& eval)
{
    if constexpr (is_evaluation<ValueType>::value)
        printEvaluation(os, eval.value(), false);
    else
        printEvaluation(os, eval, true);

    return os;
}

} // namespace DenseAd
} // namespace Opm

#include "EvaluationSpecializations.hpp"

#if HAVE_DUNE_COMMON
namespace Dune {
  template <class ValueT, int numDerivs, unsigned staticSize>
  struct IsNumber<Opm::DenseAd::Evaluation<ValueT,numDerivs,staticSize>>
    : public std::integral_constant<bool, std::is_arithmetic<ValueT>::value> {
  };
} // namespace Dune
#endif

#endif // OPM_DENSEAD_EVALUATION_HPP