// Ceres Solver - A fast non-linear least squares minimizer

// Copyright 2015 Google Inc. All rights reserved.

// http://ceres-solver.org/

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// Author: sameeragarwal@google.com (Sameer Agarwal)

#include "ceres/detect_structure.h"

#include "ceres/internal/eigen.h"

#include "glog/logging.h"

namespace ceres {

namespace internal {

void DetectStructure(const CompressedRowBlockStructure& bs,

                     const int num_eliminate_blocks,

                     int* row_block_size,

                     int* e_block_size,

                     int* f_block_size) {

  const int num_row_blocks = bs.rows.size();

  *row_block_size = 0;

  *e_block_size = 0;

  *f_block_size = 0;

  // Iterate over row blocks of the matrix, checking if row_block,

  // e_block or f_block sizes remain constant.

  for (int r = 0; r < num_row_blocks; ++r) {

    const CompressedRow& row = bs.rows[r];

    // We do not care about the sizes of the blocks in rows which do

    // not contain e_blocks.

    if (row.cells.front().block_id >= num_eliminate_blocks) {

      break;

    }

    // Detect fixed or dynamic row block size.

    if (*row_block_size == 0) {

      *row_block_size = row.block.size;

    } else if (*row_block_size != Eigen::Dynamic &&

               *row_block_size != row.block.size) {

      VLOG(2) << "Dynamic row block size because the block size changed from "

              << *row_block_size << " to "

              << row.block.size;

      *row_block_size = Eigen::Dynamic;

    }

    // Detect fixed or dynamic e-block size.

    const int e_block_id = row.cells.front().block_id;

    if (*e_block_size == 0) {

      *e_block_size = bs.cols[e_block_id].size;

    } else if (*e_block_size != Eigen::Dynamic &&

               *e_block_size != bs.cols[e_block_id].size) {

      VLOG(2) << "Dynamic e block size because the block size changed from "

              << *e_block_size << " to "

              << bs.cols[e_block_id].size;

      *e_block_size = Eigen::Dynamic;

    }

    // Detect fixed or dynamic f-block size. We are only interested in

    // rows with e-blocks, and the e-block is always the first block,

    // so only rows of size greater than 1 are of interest.

    if (row.cells.size() > 1) {

      if (*f_block_size == 0) {

        const int f_block_id = row.cells[1].block_id;

        *f_block_size = bs.cols[f_block_id].size;

      }

      for (int c = 1;

           (c < row.cells.size()) && (*f_block_size != Eigen::Dynamic);

           ++c) {

        const int f_block_id = row.cells[c].block_id;

        if (*f_block_size != bs.cols[f_block_id].size) {

          VLOG(2) << "Dynamic f block size because the block size "

                  << "changed from " << *f_block_size << " to "

                  << bs.cols[f_block_id].size;

          *f_block_size = Eigen::Dynamic;

        }

      }

    }

    const bool is_everything_dynamic = (*row_block_size == Eigen::Dynamic &&

                                        *e_block_size == Eigen::Dynamic &&

                                        *f_block_size == Eigen::Dynamic);

    if (is_everything_dynamic) {

      break;

    }

  }

  CHECK_NE(*row_block_size, 0) << "No rows found";

  CHECK_NE(*e_block_size, 0) << "No e type blocks found";

  VLOG(1) << "Schur complement static structure <"

          << *row_block_size << ","

          << *e_block_size << ","

          << *f_block_size << ">.";

}

}  // namespace internal

}  // namespace ceres