internal/ceres/array_utils.h

// 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)
//
// Utility routines for validating arrays.
//
// These are useful for detecting two common class of errors.
//
// 1. Uninitialized memory - where the user for some reason did not
// compute part of an array, but the code expects it.
//
// 2. Numerical failure while computing the cost/residual/jacobian,
// e.g. NaN, infinities etc. This is particularly useful since the
// automatic differentiation code does computations that are not
// evident to the user and can silently generate hard to debug errors.

#ifndef CERES_INTERNAL_ARRAY_UTILS_H_
#define CERES_INTERNAL_ARRAY_UTILS_H_

#include <string>
#include "ceres/internal/port.h"

namespace ceres {
namespace internal {

// Fill the array x with an impossible value that the user code is
// never expected to compute.
void InvalidateArray(int size, double* x);

// Check if all the entries of the array x are valid, i.e. all the
// values in the array should be finite and none of them should be
// equal to the "impossible" value used by InvalidateArray.
bool IsArrayValid(int size, const double* x);

// If the array contains an invalid value, return the index for it,
// otherwise return size.
int FindInvalidValue(const int size, const double* x);

// Utility routine to print an array of doubles to a string. If the
// array pointer is NULL, it is treated as an array of zeros.
void AppendArrayToString(const int size, const double* x, std::string* result);

// This routine takes an array of integer values, sorts and uniques
// them and then maps each value in the array to its position in the
// sorted+uniqued array. By doing this, if there are k unique
// values in the array, each value is replaced by an integer in the
// range [0, k-1], while preserving their relative order.
//
// For example
//
// [1 0 3 5 0 1 5]
//
// gets mapped to
//
// [1 0 2 3 0 1 3]
void MapValuesToContiguousRange(int size, int* array);

}  // namespace internal
}  // namespace ceres

#endif  // CERES_INTERNAL_ARRAY_UTILS_H_