/*
Copyright 2015-2022 Ian Jauslin

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

/*
Compute the mean of a monomial or a polynomial
*/

#ifndef MEAN_H
#define MEAN_H

#include "types.h"

// mean of a monomial
int mean(Int_Array monomial, Polynomial* out, Fields_Table fields, Polynomial_Matrix propagator);

// compute the mean of a monomial of internal fields (with split + and -)
int mean_internal(Int_Array internal_plus, Int_Array internal_minus, Polynomial* out, Polynomial_Matrix propagator, Fields_Table fields);

// compute the mean of a monomial by computing a determinant
int mean_determinant(Int_Array internal_plus, Int_Array internal_minus, Number* out, Polynomial_Matrix propagator,Fields_Table fields);

// compute the mean of a monomial by summing over permutations
int mean_permutations(Int_Array internal_plus, Int_Array internal_minus, Polynomial* out, Polynomial_Matrix propagator, Fields_Table fields);
// first pairing with a non-vanishing propagator
int init_pairing(int* pairing, int* mask, int n, Polynomial_Matrix propagator, int* indices_plus, int* indices_minus);
// next pairing with a non-vanishing propagator
int next_pairing(int* pairing, int* mask, int n, Polynomial_Matrix propagator, int* indices_plus, int* indices_minus);
// next term in the Wick expansion
int next_wick(int index, int start, int* mask, int n, Polynomial_Matrix propagator, int* indices_plus, int* indices_minus);

/*
int mean_internal_slow(Int_Array internal_plus, Int_Array internal_minus, Number* outnum, Polynomial_Matrix propagator);
*/

// get lists of internal fields from a monomial (separate + and -)
// requires the monomial to be sorted (for the sign to be correct)
int get_internals(Int_Array monomial, Int_Array* internal_plus, Int_Array* internal_minus, Int_Array* others, Fields_Table fields);

// compute the mean of a monomial containing virtual fields
int mean_virtual_fields(Int_Array monomial, Polynomial* output, Fields_Table fields, Polynomial_Matrix propagator, Groups groups, Identities* computed);
// first term in product with no repetitions
int init_prod(int* current_term, Int_Array virtual_field_list, Fields_Table fields, int power, Int_Array base_monomial);
// next term in product with no repetitions
int next_prod(int* current_term, Int_Array virtual_field_list, Fields_Table fields, int power, Int_Array base_monomial);
// find the next term in a polynomial that can be multiplied to a given monomial and add it to the monomial
int next_term_norepeat(int start, Polynomial polynomial, Int_Array* monomial, Fields_Table fields);

// signature of a permutation
int permutation_signature(int* permutation, int n);

// sort a list of anti-commuting variables
int sort_fermions(int* array, int begin, int end, int* sign);

// mean while factoring groups out
int mean_groups(Int_Array monomial, Polynomial* output, Fields_Table fields, Polynomial_Matrix propagator, Groups groups, Identities* computed);

// compute the mean of a polynomial
int polynomial_mean(Polynomial* polynomial, Fields_Table fields, Polynomial_Matrix propagator, Groups groups, int print_progress);
// multithreaded
int polynomial_mean_multithread(Polynomial* polynomial, Fields_Table fields, Polynomial_Matrix propagator, Groups groups, int threads, int print_progress);
// single thread mean
void* polynomial_mean_thread(void* mean_args);
#endif