// 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_ELIMINATE_NOPS_H_
#define CERES_PUBLIC_CODEGEN_INTERNAL_ELIMINATE_NOPS_H_

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

namespace ceres {
namespace internal {

// [OptimizationPass] NOP Cleanup
//
// Short Description:
//   Removes all expression with type==ExpressionType::NOP.
//
// Description:
//   Removing an expression not at the end requires reindexing of all later
//   expressions. Therefore, other optimization passes replace expression with
//   NOP instead of removing them. This optimization pass removes all NOPs back
//   to front.
//   The returned value is equal to the number of removed NOPs.
//
// Example:
//   v_0 = 1;
//   // NOP
//   v_2 = 2;
//   v_3 = v_0 + v_2
// Transforms to:
//   v_0 = 1;
//   v_1 = 2;
//   v_2 = v_0 + v_1;

OptimizationPassSummary EliminateNops(ExpressionGraph* graph);

}  // namespace internal
}  // namespace ceres

#endif  // CERES_PUBLIC_CODEGEN_INTERNAL_ELIMINATE_NOPS_H_