github.com/consensys/gnark-crypto@v0.14.0/ecc/bn254/fr/iop/expressions.go (about)

     1  // Copyright 2020 Consensys Software Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // Code generated by consensys/gnark-crypto DO NOT EDIT
    16  
    17  package iop
    18  
    19  import (
    20  	"errors"
    21  	"github.com/consensys/gnark-crypto/ecc/bn254/fr"
    22  	"github.com/consensys/gnark-crypto/internal/parallel"
    23  	"math/bits"
    24  )
    25  
    26  // Expression represents a multivariate polynomial.
    27  type Expression func(i int, x ...fr.Element) fr.Element
    28  
    29  // Evaluate evaluates f on each entry of x. The returned value is
    30  // the vector of evaluations of e on x.
    31  // The form of the result is form.
    32  // if r is provided (not nil), it is used as the result vector,
    33  // that is the memory space for the coefficients of the resulting polynomial.
    34  // The Size field of the result is the same as the one of x[0].
    35  // The blindedSize field of the result is the same as Size.
    36  // The Shift field of the result is 0.
    37  func Evaluate(f Expression, r []fr.Element, form Form, x ...*Polynomial) (*Polynomial, error) {
    38  	if len(x) == 0 {
    39  		return nil, errors.New("need at lest one input")
    40  	}
    41  
    42  	// check that the sizes are consistent
    43  	n := x[0].coefficients.Len()
    44  	m := len(x)
    45  	for i := 1; i < m; i++ {
    46  		if n != x[i].coefficients.Len() {
    47  			return nil, ErrInconsistentSize
    48  		}
    49  	}
    50  
    51  	// check result len
    52  	if r == nil {
    53  		r = make([]fr.Element, n)
    54  	} else if len(r) != n {
    55  		return nil, ErrInconsistentSize
    56  	}
    57  
    58  	// result coefficients
    59  	idx := func(i int) int {
    60  		return i
    61  	}
    62  	if form.Layout != Regular {
    63  		nn := uint64(64 - bits.TrailingZeros(uint(n)))
    64  		idx = func(i int) int {
    65  			return int(bits.Reverse64(uint64(i)) >> nn)
    66  		}
    67  	}
    68  
    69  	parallel.Execute(n, func(start, end int) {
    70  		vx := make([]fr.Element, m)
    71  		for i := start; i < end; i++ {
    72  			for j := 0; j < m; j++ {
    73  				vx[j] = x[j].GetCoeff(i)
    74  			}
    75  			r[idx(i)] = f(i, vx...)
    76  		}
    77  	})
    78  
    79  	res := NewPolynomial(&r, form)
    80  	res.size = x[0].size
    81  	res.blindedSize = x[0].size
    82  	res.shift = 0
    83  
    84  	return res, nil
    85  }