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<doc>
   <title>Optimization</title>

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   <body>
      <br/><br/>

         <p>
            This page documents library components that attempt to find the 
            minimum or maximum of a user supplied function.   An introduction
            to the general purpose non-linear optimizers in this section can be
            found <a href="optimization_ex.cpp.html">here</a>.  For an example
            showing how to use the non-linear least squares routines look 
            <a href="least_squares_ex.cpp.html">here</a>.
         </p>

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   <menu width="150">
    <top>
      <section>
         <name>Main Routines</name>
         <item>find_min</item> 
         <item>find_min_single_variable</item> 
         <item>find_min_using_approximate_derivatives</item> 
         <item>find_min_bobyqa</item> 
         <item>solve_qp_using_smo</item> 
         <item>solve_qp2_using_smo</item> 
         <item>oca</item> 
         <item>find_max</item> 
         <item>find_max_single_variable</item> 
         <item>find_max_using_approximate_derivatives</item> 
         <item>find_max_bobyqa</item> 
         <item>find_max_trust_region</item> 
         <item>find_min_trust_region</item> 
         <item>solve_least_squares</item> 
         <item>solve_least_squares_lm</item> 
      </section>

      <section>
         <name>Strategies</name>
         <item>cg_search_strategy</item>
         <item>bfgs_search_strategy</item>
         <item>newton_search_strategy</item>
         <item>lbfgs_search_strategy</item>
         <item>objective_delta_stop_strategy</item>
         <item>gradient_norm_stop_strategy</item>
      </section>

      <section>
         <name>Helper Routines</name>
         <item>derivative</item> 
         <item>negate_function</item> 
         <item>make_line_search_function</item> 
         <item>poly_min_extrap</item> 
         <item>lagrange_poly_min_extrap</item> 
         <item>line_search</item> 
         <item>solve_trust_region_subproblem</item> 
      </section>

    </top>  
   </menu>

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   <components>
   
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      <component>
         <name>derivative</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_abstract.h</spec_file>
         <description>
            This is a function that takes another function as input and returns
            a function object that numerically computes the derivative of the input function.
         </description>
                                 
      </component>


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      <component>
         <name>negate_function</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_abstract.h</spec_file>
         <description>
            This is a function that takes another function as input and returns
            a function object that computes the negation of the input function.
         </description>
                                 
      </component>


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      <component>
         <name>make_line_search_function</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_line_search_abstract.h</spec_file>
         <description>
            This is a function that takes another function f(x) as input and returns
            a function object l(z) = f(start + z*direction).   It is useful for
            turning multi-variable functions into single-variable functions for
            use with the <a href="#line_search">line_search</a> routine.
         </description>
                                 
      </component>


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      <component>
         <name>poly_min_extrap</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_line_search_abstract.h</spec_file>
         <description>
            This function finds the 3rd degree polynomial that interpolates a 
            set of points and returns you the minimum of that polynomial.
         </description>
                                 
      </component>

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      <component>
         <name>lagrange_poly_min_extrap</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_line_search_abstract.h</spec_file>
         <description>
            This function finds the second order polynomial that interpolates a 
            set of points and returns you the minimum of that polynomial.
         </description>
                                 
      </component>

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      <component>
         <name>line_search</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_line_search_abstract.h</spec_file>
         <description>
            Performs a gradient based line search on a given function and returns the input
            that makes the function significantly smaller.
         </description>
                                 
      </component>


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      <component>
         <name>cg_search_strategy</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_search_strategies_abstract.h</spec_file>
         <description>
                This object represents a strategy for determining which direction
                a <a href="#line_search">line search</a> should be carried out along.  This particular object
                is an implementation of the Polak-Ribiere conjugate gradient method
                for determining this direction.

                  <p>
                This method uses an amount of memory that is linear in the number
                of variables to be optimized.  So it is capable of handling problems
                with a very large number of variables.  However, it is generally
                not as good as the L-BFGS algorithm (see the 
                <a href="#lbfgs_search_strategy">lbfgs_search_strategy</a> class).
                  </p>
         </description>
         <examples>
            <example>optimization_ex.cpp.html</example>
         </examples>
                                 
      </component>

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      <component>
         <name>bfgs_search_strategy</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_search_strategies_abstract.h</spec_file>
         <description>
                This object represents a strategy for determining which direction
                a <a href="#line_search">line search</a> should be carried out along.  This particular object
                is an implementation of the BFGS quasi-newton method for determining 
                this direction.

                  <p>
                This method uses an amount of memory that is quadratic in the number
                of variables to be optimized.  It is generally very effective but 
                if your problem has a very large number of variables then it isn't 
                appropriate.  Instead, you should try the <a href="#lbfgs_search_strategy">lbfgs_search_strategy</a>.
                  </p>
         </description>
         <examples>
            <example>optimization_ex.cpp.html</example>
         </examples>
                                 
      </component>

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      <component>
         <name>newton_search_strategy</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_search_strategies_abstract.h</spec_file>
         <description>
                This object represents a strategy for determining which direction
                a <a href="#line_search">line search</a> should be carried out along.  This particular routine 
                is an implementation of the newton method for determining this direction.  
                That means using it requires you to supply a method for
                creating hessian matrices for the problem you are trying to optimize.

               <p>
               Note also that this is actually a helper function for creating 
               <a href="dlib/optimization/optimization_search_strategies_abstract.h.html#newton_search_strategy_obj"
                     >newton_search_strategy_obj</a> objects.  
               </p>

         </description>
                                 
      </component>

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      <component>
         <name>lbfgs_search_strategy</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_search_strategies_abstract.h</spec_file>
         <description>
                This object represents a strategy for determining which direction
                a <a href="#line_search">line search</a> should be carried out along.  This particular object
                is an implementation of the L-BFGS quasi-newton method for determining 
                this direction.

                  <p>
                This method uses an amount of memory that is linear in the number
                of variables to be optimized.  This makes it an excellent method 
                to use when an optimization problem has a large number of variables.
                  </p>
         </description>
         <examples>
            <example>optimization_ex.cpp.html</example>
         </examples>
                                 
      </component>

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      <component>
         <name>objective_delta_stop_strategy</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_stop_strategies_abstract.h</spec_file>
         <description>
                This object represents a strategy for deciding if an optimization
                algorithm should terminate.   This particular object looks at the 
                change in the objective function from one iteration to the next and 
                bases its decision on how large this change is.  If the change
                is below a user given threshold then the search stops.
         </description>
         <examples>
            <example>optimization_ex.cpp.html</example>
         </examples>
                                 
      </component>

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      <component>
         <name>gradient_norm_stop_strategy</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_stop_strategies_abstract.h</spec_file>
         <description>
                This object represents a strategy for deciding if an optimization
                algorithm should terminate.   This particular object looks at the 
                norm (i.e. the length) of the current gradient vector and
                stops if it is smaller than a user given threshold.  
         </description>
                                 
      </component>

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      <component>
         <name>find_min</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_abstract.h</spec_file>
         <description>
             Performs an unconstrained minimization of a nonlinear function using 
             some search strategy (e.g. <a href="#bfgs_search_strategy">bfgs_search_strategy</a>).
         </description>
         <examples>
            <example>optimization_ex.cpp.html</example>
         </examples>
                                 
      </component>

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      <component>
         <name>find_min_single_variable</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_line_search_abstract.h</spec_file>
         <description>
             Performs a bound constrained minimization of a nonlinear function.  The 
             function must be of a single variable.  Derivatives are not required.  
         </description>
                                 
      </component>

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      <component>
         <name>solve_trust_region_subproblem</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_trust_region_abstract.h</spec_file>
         <description>
             This function solves the following optimization problem:
<pre>
Minimize: f(p) == 0.5*trans(p)*B*p + trans(g)*p
subject to the following constraint:
   length(p) &lt;= radius
</pre>

         </description>
                                 
      </component>

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      <component>
         <name>solve_qp_using_smo</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_solve_qp_using_smo_abstract.h</spec_file>
         <description>
             This function solves the following quadratic program:
<pre>
   Minimize: f(alpha) == 0.5*trans(alpha)*Q*alpha - trans(alpha)*b
   subject to the following constraints:
      sum(alpha) == C 
      min(alpha) >= 0 
   Where f is convex.  This means that Q should be symmetric and positive-semidefinite.
</pre>

         </description>
                                 
      </component>

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      <component>
         <name>solve_qp2_using_smo</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_solve_qp2_using_smo_abstract.h</spec_file>
         <description>
             This function solves the following quadratic program:
<pre>
   Minimize: f(alpha) == 0.5*trans(alpha)*Q*alpha 
   subject to the following constraints:
      sum(alpha) == nu*y.size() 
      0 &lt;= min(alpha) &amp;&amp; max(alpha) &lt;= 1 
      trans(y)*alpha == 0

   Where all elements of y must be equal to +1 or -1 and f is convex.  
   This means that Q should be symmetric and positive-semidefinite.
</pre>
<br/>
                This object implements the strategy used by the LIBSVM tool.  The following papers
                can be consulted for additional details:
               <ul>
                  <li>Chang and Lin, Training {nu}-Support Vector Classifiers: Theory and Algorithms</li>
                  <li>Chih-Chung Chang and Chih-Jen Lin, LIBSVM : a library for support vector 
                     machines, 2001. Software available at 
                     <a href="http://www.csie.ntu.edu.tw/~cjlin/libsvm">http://www.csie.ntu.edu.tw/~cjlin/libsvm</a></li>
               </ul>

         </description>
                                 
      </component>

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      <component>
         <name>oca</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_oca_abstract.h</spec_file>
         <description>
                This object is a tool for solving the following optimization problem:   
<pre>
   Minimize: f(w) == 0.5*dot(w,w) + C*R(w)

   Where R(w) is a user-supplied convex function and C > 0
</pre>
<br/>
<br/>

                For a detailed discussion you should consult the following papers
                from the Journal of Machine Learning Research:
                <blockquote>
                    Optimized Cutting Plane Algorithm for Large-Scale Risk Minimization
                      by  Vojtech Franc, Soren Sonnenburg; 10(Oct):2157--2192, 2009. 
                </blockquote>
                <blockquote>
                    Bundle Methods for Regularized Risk Minimization
                      by Choon Hui Teo, S.V.N. Vishwanthan, Alex J. Smola, Quoc V. Le; 11(Jan):311-365, 2010. 
                </blockquote>

         </description>
                                 
      </component>

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      <component>
         <name>find_min_bobyqa</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_bobyqa_abstract.h</spec_file>
         <description>
            This function defines the dlib interface to the BOBYQA software developed by M.J.D Powell.
            BOBYQA is a method for optimizing a function in the absence of derivative information.  
            Powell described it as a method that seeks the least value of a function of many 
            variables, by applying a trust region method that forms quadratic models by 
            interpolation.  There is usually some freedom in the interpolation conditions, 
            which is taken up by minimizing the Frobenius norm of the change to the second 
            derivative of the model, beginning with the zero matrix. The values of the variables 
            are constrained by upper and lower bounds.  

            <p>
            The following paper, published in 2009 by Powell, describes the
            detailed working of the BOBYQA algorithm.  

               <blockquote>
               The BOBYQA algorithm for bound constrained optimization 
               without derivatives by M.J.D. Powell
               </blockquote>
            </p>

            <p>
               Note that BOBYQA only works on functions of two or more variables.  So if you need to perform 
               derivative-free optimization on a function of a single variable 
               then you should use the <a href="#find_min_single_variable">find_min_single_variable</a>
               function.
            </p>

         </description>
         <examples>
            <example>optimization_ex.cpp.html</example>
            <example>model_selection_ex.cpp.html</example>
         </examples>
                                 
      </component>

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      <component>
         <name>find_max_bobyqa</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_bobyqa_abstract.h</spec_file>
         <description>
            This function is identical to the <a href="#find_min_bobyqa">find_min_bobyqa</a> routine 
            except that it negates the objective function before performing optimization.  
            Thus this function will attempt to find the maximizer of the objective rather than 
            the minimizer.
            <p>
               Note that BOBYQA only works on functions of two or more variables.  So if you need to perform 
               derivative-free optimization on a function of a single variable 
               then you should use the <a href="#find_max_single_variable">find_max_single_variable</a>
               function.
            </p>
         </description>
         <examples>
            <example>optimization_ex.cpp.html</example>
            <example>model_selection_ex.cpp.html</example>
         </examples>
                                 
      </component>

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      <component>
         <name>find_min_using_approximate_derivatives</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_abstract.h</spec_file>
         <description>
             Performs an unconstrained minimization of a nonlinear function using 
             some search strategy (e.g. <a href="#bfgs_search_strategy">bfgs_search_strategy</a>).
             This version doesn't take a gradient function but instead numerically approximates 
             the gradient.
         </description>
         <examples>
            <example>optimization_ex.cpp.html</example>
         </examples>
                                 
      </component>

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      <component>
         <name>solve_least_squares</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_least_squares_abstract.h</spec_file>
         <description>
            This is a function for solving non-linear least squares problems.  It uses a method
            which combines the traditional Levenberg-Marquardt technique with a quasi-newton
            approach.  It is appropriate for large residual problems (i.e. problems where the
            terms in the least squares function, the residuals, don't go to zero but remain
            large at the solution)
         </description>
                                 
         <examples>
            <example>least_squares_ex.cpp.html</example>
         </examples>
      </component>

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      <component>
         <name>solve_least_squares_lm</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_least_squares_abstract.h</spec_file>
         <description>
            This is a function for solving non-linear least squares problems.  It uses 
            the traditional Levenberg-Marquardt technique. 
            It is appropriate for small residual problems (i.e. problems where the
            terms in the least squares function, the residuals, go to zero at the solution)
         </description>
                                 
         <examples>
            <example>least_squares_ex.cpp.html</example>
         </examples>
      </component>

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      <component>
         <name>find_min_trust_region</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_trust_region_abstract.h</spec_file>
         <description>
             Performs an unconstrained minimization of a nonlinear function using 
             a trust region method.
         </description>
                                 
      </component>

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      <component>
         <name>find_max_trust_region</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_trust_region_abstract.h</spec_file>
         <description>
             Performs an unconstrained maximization of a nonlinear function using 
             a trust region method.
         </description>
                                 
      </component>

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      <component>
         <name>find_max</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_abstract.h</spec_file>
         <description>
             Performs an unconstrained maximization of a nonlinear function using 
             some search strategy (e.g. <a href="#bfgs_search_strategy">bfgs_search_strategy</a>).
         </description>
                                 
      </component>

   <!-- ************************************************************************* -->
      
      <component>
         <name>find_max_single_variable</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_line_search_abstract.h</spec_file>
         <description>
             Performs a bound constrained maximization of a nonlinear function.  The 
             function must be of a single variable.  Derivatives are not required.
         </description>
                                 
      </component>

   <!-- ************************************************************************* -->
      
      <component>
         <name>find_max_using_approximate_derivatives</name>
         <file>dlib/optimization.h</file>
         <spec_file link="true">dlib/optimization/optimization_abstract.h</spec_file>
         <description>
             Performs an unconstrained maximization of a nonlinear function using 
             some search strategy (e.g. <a href="#bfgs_search_strategy">bfgs_search_strategy</a>).
             This version doesn't take a gradient function but instead numerically approximates 
             the gradient.
         </description>
                                 
      </component>

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   </components>

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</doc>

