include/ceres/codegen/internal/optimize_expression_graph.h

// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2020 Google Inc. All rights reserved.
// http://code.google.com/p/ceres-solver/
//
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//
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// Author: darius.rueckert@fau.de (Darius Rueckert)
//
#ifndef CERES_PUBLIC_CODEGEN_INTERNAL_OPTIMIZE_EXPRESSION_GRAPH_H_
#define CERES_PUBLIC_CODEGEN_INTERNAL_OPTIMIZE_EXPRESSION_GRAPH_H_

#include <memory>
#include <vector>

#include "ceres/codegen/internal/expression_graph.h"
#include "ceres/codegen/internal/optimization_pass_summary.h"

namespace ceres {
namespace internal {

struct OptimizeExpressionGraphOptions {
  int max_num_iterations = 100;
  bool eliminate_nops = true;
};

struct OptimizeExpressionGraphSummary {
  int num_iterations;
  std::vector<OptimizationPassSummary> summaries;
};

// Optimize the given ExpressionGraph in-place according to the defined
// OptimizeExpressionGraphOptions. This will change the ExpressionGraph, but the
// generated code will output the same numerical values.
//
// The Optimization iteratively applies all OptimizationPasses until the graph
// does not change anymore or max_num_iterations is reached. Pseudo Code:
//
//   for(int it = 0; it < max_num_iterations; ++it) {
//      graph.hasChanged = false;
//      for each pass in OptimizationPasses
//         pass.applyTo(graph)
//      if(!graph.hasChanged)
//         break;
//   }
//
OptimizeExpressionGraphSummary OptimizeExpressionGraph(
    const OptimizeExpressionGraphOptions& options, ExpressionGraph* graph);

}  // namespace internal
}  // namespace ceres

#endif  // CERES_PUBLIC_CODEGEN_INTERNAL_OPTIMIZE_EXPRESSION_GRAPH_H_