DynamicEvaluation.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_DYNAMIC_HPP
#define OPM_DENSEAD_EVALUATION_DYNAMIC_HPP

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

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

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

namespace Opm {
namespace DenseAd {

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

    typedef ValueT ValueType;

    OPM_HOST_DEVICE int size() const
    { return data_.size() - 1; }

protected:
    OPM_HOST_DEVICE int length_() const
    { return data_.size(); }


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

    OPM_HOST_DEVICE constexpr void checkDefined_() const
    {
#ifndef NDEBUG
        for (int i = dstart_(); i < dend_(); ++i)
            Valgrind::CheckDefined(data_[i]);
#endif
    }

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

    Evaluation(const Evaluation& other) = default;

    OPM_HOST_DEVICE Evaluation(Evaluation&& other)
        : data_(std::move(other.data_))
    { }

    OPM_HOST_DEVICE Evaluation& operator=(Evaluation&& other)
    {
        data_ = std::move(other.data_);
        return *this;
    }

    // create a dynamic 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 Evaluation(int numDerivatives, const RhsValueType& c)
        : data_(1 + numDerivatives, 0.0)
    {
        //clearDerivatives();
        setValue(c);

        checkDefined_();
    }

    // create a dynamic evaluation which represents a constant function
    // by using zero number of derivatives.
    //
    // i.e., f(x) = c. this implies an evaluation with the given value and all
    // derivatives being zero.
    template <class RhsValueType>
    OPM_HOST_DEVICE Evaluation(const RhsValueType& c)
        : Evaluation(0, c)
    {
    }

    // 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(int nVars, const RhsValueType& c, int varPos)
        : data_(1 + nVars, 0.0)
    {
        // The variable position must be in represented by the given variable descriptor
        assert(0 <= varPos && varPos < size());

        setValue(c);

        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& x)
    { return Evaluation(x.size()); }

    // create an Evaluation with value and all the derivatives to be zero
    OPM_HOST_DEVICE static Evaluation createConstantZero(const Evaluation& x)
    { return Evaluation(x.size(), 0.0); }

    // create an Evaluation with value to be one and all the derivatives to be zero
    OPM_HOST_DEVICE static Evaluation createConstantOne(const Evaluation& x)
    { return Evaluation(x.size(), 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&, int)
    {
        throw std::logic_error("Dynamically sized evaluations require that the number of "
                               "derivatives is specified when creating an evaluation");
    }

    template <class RhsValueType>
    OPM_HOST_DEVICE static Evaluation createVariable(int nVars, 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(nVars, value, varPos);
    }

    template <class RhsValueType>
    OPM_HOST_DEVICE static Evaluation createVariable(const Evaluation& x, 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(x.size(), 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)
    {
        return Evaluation(nVars, 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)
    {
        // using an evaluation without 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 Evaluation& x, const RhsValueType& value)
    {
        return Evaluation(x.size(), 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)
    {
        const int thisSize = size();
        const int otherSize = other.size();

        // Allow operation if sizes match or one is constant (size == 0)
        assert(thisSize == otherSize || thisSize == 0 || otherSize == 0);

        if (thisSize == otherSize) {
            for (int i = 0; i < length_(); ++i)
                data_[i] += other.data_[i];
            return *this;
        }
        if (otherSize == 0) {
            *this += other.value();
            return *this;
        }
        if (thisSize == 0) {
            assert(otherSize > 0);
            this->appendDerivativesToConstant(otherSize);
            data_[valuepos_()] += other.data_[valuepos_()];
            for (int i = dstart_(); i < dend_(); ++i)
                data_[i] = other.data_[i];
            return *this;
        }
        throw std::logic_error(
                "Cannot operate Evaluations with different number of derivatives "
                "unless one of them has no derivatives"
        );
    }

    // 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)
    {
        const int thisSize = size();
        const int otherSize = other.size();

        // Allow operation if sizes match or one is constant (size == 0)
        assert(thisSize == otherSize || thisSize == 0 || otherSize == 0);

        if (thisSize == otherSize) {
            for (int i = 0; i < length_(); ++i)
                data_[i] -= other.data_[i];
            return *this;
        }
        if (otherSize == 0) {
            *this -= other.value();
            return *this;
        }
        if (thisSize == 0) {
            assert(otherSize > 0);
            this->appendDerivativesToConstant(otherSize);
            for (int i = 0; i < other.length_(); ++i)
                data_[i] -= other.data_[i];
            return *this;
        }
        throw std::logic_error(
                "Cannot operate Evaluations with different number of derivatives "
                "unless one of them has no derivatives"
        );
    }

    // 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)
    {
        const int thisSize = size();
        const int otherSize = other.size();

        // Allow operation if sizes match or one is constant (size == 0)
        assert(thisSize == otherSize || thisSize == 0 || otherSize == 0);

        if (thisSize == otherSize) {
            // 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;
        }

        if (otherSize == 0) {
            *this *= other.value();
            return *this;
        }

        if (thisSize == 0) {
            assert(otherSize > 0);
            this->appendDerivativesToConstant(otherSize);
            const ValueType u = this->value();
            for (int i = 0; i < length_(); ++i) {
                data_[i] = u * other.data_[i];
            }
            return *this;
        }
        throw std::logic_error(
                "Cannot operate Evaluations with different number of derivatives "
                "unless one of them has no derivatives"
        );
    }

    // 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)
    {
        const int thisSize = size();
        const int otherSize = other.size();

        // Allow operation if sizes match or one is constant (size == 0)
        assert(thisSize == otherSize || thisSize == 0 || otherSize == 0);

        if (thisSize == otherSize) {
            // while the values are divided, the 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();

            // derivatives
            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);
            }

            // value
            u /= v;

            return *this;
        }

        if (otherSize == 0) {
            *this /= other.value();
            return *this;
        }

        if (thisSize == 0) {
            assert(otherSize > 0);
            // if *this is a constant, extend to hold derivatives before division
            this->appendDerivativesToConstant(otherSize);

            // 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& vPrime = other.data_[idx];
                data_[idx] =  -u * vPrime / (v * v);
            }
            u /= v;

            return *this;
        }
        throw std::logic_error(
                "Cannot operate Evaluations with different number of derivatives "
                "unless one of them has no derivatives"
        );
    }

    // 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
    {
#ifndef NDEBUG
        const int thisSize = size();
        const int otherSize = other.size();

        // Allow operation if sizes match or one is constant (size == 0)
        assert(thisSize == otherSize || thisSize == 0 || otherSize == 0);
#endif

        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
    {
#ifndef NDEBUG
        const int thisSize = size();
        const int otherSize = other.size();

        // Allow operation if sizes match or one is constant (size == 0)
        assert(thisSize == otherSize || thisSize == 0 || otherSize == 0);
#endif

        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(*this);

        // 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
    {
#ifndef NDEBUG
        const int thisSize = size();
        const int otherSize = other.size();

        // Allow operation if sizes match or one is constant (size == 0)
        assert(thisSize == otherSize || thisSize == 0 || otherSize == 0);
#endif

        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
    {
#ifndef NDEBUG
        const int thisSize = size();
        const int otherSize = other.size();

        // Allow operation if sizes match or one is constant (size == 0)
        assert(thisSize == otherSize || thisSize == 0 || otherSize == 0);
#endif

        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
    {
        const int thisSize = size();
        const int otherSize = other.size();

        // Allow operation if sizes match or one is constant (size == 0)
        assert(thisSize == otherSize || thisSize == 0 || otherSize == 0);

        if (thisSize == otherSize) {
            for (int idx = 0; idx < length_(); ++idx) {
                if (data_[idx] != other.data_[idx]) {
                    return false;
                }
            }
        } else {
            return value() == other.value();
        }
        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() || size() == 0 || other.size() == 0);

        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() || size() == 0 || other.size() == 0);

        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() || size() == 0 || other.size() == 0);

        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() || size() == 0 || other.size() == 0);

        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)
    {
        if (data_.size() == 0) {
            data_.resize(1);
        }
        data_[valuepos_()] = val;
    }

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

        if (size() == 0) {
            static const ValueType zero {0.0};
            return zero;
        }

        return data_[dstart_() + varIdx];
    }

    // set derivative at position varIdx
    OPM_HOST_DEVICE void setDerivative(int varIdx, const ValueType& derVal, const int nVars = -1)
    {
        // if size() == 0, we need nVars to be positive to extend the number of derivatives
        // if size() > 0, nVars must be either negative (i.e. ignore) or match size()
        assert( (size() == 0 && nVars > 0) ||
                ((size() > 0 && (nVars < 0 || nVars == size()))) );

        if (size() == 0) {
            if (nVars < 0) {
                throw std::logic_error("Cannot set derivative for a DynamicEvaluation initialized from a scalar "
                                       "without specifying a positive number of derivatives");
            }

            this->appendDerivativesToConstant(nVars);
        }

        assert(0 <= varIdx && varIdx < size());

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

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

private:
    FastSmallVector<ValueT, staticSize> data_;

    void appendDerivativesToConstant(size_t numDer) {
        assert(size() == 0); // we only append derivatives to a constant
        if (numDer > 0) {
            data_.resize(1 + numDer);
        }
    }
};

template <class Scalar, unsigned staticSize = 0>
using DynamicEvaluation = Evaluation<Scalar, DynamicSize, staticSize>;

} // namespace DenseAd

template <class Scalar, unsigned staticSize>
OPM_HOST_DEVICE DenseAd::Evaluation<Scalar, -1, staticSize> constant(int numDerivatives, const Scalar& value)
{ return DenseAd::Evaluation<Scalar, -1, staticSize>::createConstant(numDerivatives, value); }

template <class Scalar, unsigned staticSize>
OPM_HOST_DEVICE DenseAd::Evaluation<Scalar, -1, staticSize> variable(int numDerivatives, const Scalar& value, unsigned idx)
{ return DenseAd::Evaluation<Scalar, -1, staticSize>::createVariable(numDerivatives, value, idx); }

} // namespace Opm

#endif // OPM_DENSEAD_EVALUATION_DYNAMIC_HPP