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<option>AD Function</option>
<option>AD of Base</option>
<option>AD Levels Above Base</option>
<option>Base Function</option>
<option>Base Type</option>
<option>Elementary Vector</option>
<option>Operation</option>
<option>---..Atomic</option>
<option>---..Sequence</option>
<option>---..Dependent</option>
<option>---..Independent</option>
<option>Parameter</option>
<option>Sparsity Pattern</option>
<option>---..Vector of Boolean</option>
<option>---..Vector of Sets</option>
<option>Tape</option>
<option>---..Active</option>
<option>---..Inactive</option>
<option>---..Independent Variable</option>
<option>---..Dependent Variables</option>
<option>Taylor Coefficient</option>
<option>Variable</option>
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<center><b><big><big>Glossary</big></big></b></center>
<br/>
<b><big><a name="AD Function" id="AD Function">AD Function</a></big></b>
<br/>
Given an <a href="adfun.xml" target="_top"><span style='white-space: nowrap'>ADFun</span></a>
object
<code><i><font color="black"><span style='white-space: nowrap'>f</span></font></i></code>
there is a corresponding
AD of
<code><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i></code>
<a href="glossary.xml#Operation.Sequence" target="_top"><span style='white-space: nowrap'>operation sequence</span></a>
.
This operation sequence
defines a function
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>F</mi>
<mo stretchy="false">:</mo>
<msup><mi mathvariant='italic'>B</mi>
<mi mathvariant='italic'>n</mi>
</msup>
<mo stretchy="false">→</mo>
<msup><mi mathvariant='italic'>B</mi>
<mi mathvariant='italic'>m</mi>
</msup>
</mrow></math>
where
<code><i><font color="black"><span style='white-space: nowrap'>B</span></font></i></code>
is the space corresponding to objects of type
<code><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i></code>
,
<code><i><font color="black"><span style='white-space: nowrap'>n</span></font></i></code>
is the size of the <a href="seq_property.xml#Domain" target="_top"><span style='white-space: nowrap'>domain</span></a>
space, and
<code><i><font color="black"><span style='white-space: nowrap'>m</span></font></i></code>
is the size of the <a href="seq_property.xml#Range" target="_top"><span style='white-space: nowrap'>range</span></a>
space.
We refer to
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>F</mi>
</mrow></math>
as the AD function corresponding to
the operation sequence stored in the object
<code><i><font color="black"><span style='white-space: nowrap'>f</span></font></i></code>
.
(See the <a href="funcheck.xml#Discussion" target="_top"><span style='white-space: nowrap'>FunCheck discussion</span></a>
for
possible differences between
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>F</mi>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>x</mi>
<mo stretchy="false">)</mo>
</mrow></math>
and the algorithm that defined
the operation sequence.)
<br/>
<br/>
<b><big><a name="AD of Base" id="AD of Base">AD of Base</a></big></b>
<br/>
An object is called an AD of
<code><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i></code>
object its type is
either
<code><font color="blue"><span style='white-space: nowrap'>AD<</span></font><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i><font color="blue"><span style='white-space: nowrap'>></span></font></code>
(see the default and copy <a href="ad_ctor.xml" target="_top"><span style='white-space: nowrap'>constructors</span></a>
or
<code><font color="blue"><span style='white-space: nowrap'>VecAD<</span></font><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i><font color="blue"><span style='white-space: nowrap'>>::reference</span></font></code>
(see <a href="vecad.xml" target="_top"><span style='white-space: nowrap'>VecAD</span></a>
)
for some
<code><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i></code>
type.
<br/>
<br/>
<b><big><a name="AD Levels Above Base" id="AD Levels Above Base">AD Levels Above Base</a></big></b>
<br/>
If
<code><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i></code>
is a type,
the AD levels above
<code><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i></code>
is the following sequence of types:
<code><font color="blue"><span style='white-space: nowrap'><br/>
     AD<</span></font><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i><font color="blue"><span style='white-space: nowrap'>> </span></font><i><font color="black"><span style='white-space: nowrap'>,</span></font></i><font color="blue"><span style='white-space: nowrap'> AD< AD<</span></font><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i><font color="blue"><span style='white-space: nowrap'>> > </span></font><i><font color="black"><span style='white-space: nowrap'>,</span></font></i><font color="blue"><span style='white-space: nowrap'> AD< AD< AD<</span></font><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i><font color="blue"><span style='white-space: nowrap'>> > > </span></font><i><font color="black"><span style='white-space: nowrap'>,</span></font></i><font color="blue"><span style='white-space: nowrap'> </span></font><i><font color="black"><span style='white-space: nowrap'>...</span></font></i><font color="blue"><span style='white-space: nowrap'><br/>
</span></font></code>
<br/>
<b><big><a name="Base Function" id="Base Function">Base Function</a></big></b>
<br/>
A function
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>f</mi>
<mo stretchy="false">:</mo>
<mi mathvariant='italic'>B</mi>
<mo stretchy="false">→</mo>
<mi mathvariant='italic'>B</mi>
</mrow></math>
is referred to as a
<code><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i></code>
function,
if
<code><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i></code>
is a C++ type that represent elements of
the domain and range space of
<code><i><font color="black"><span style='white-space: nowrap'>f</span></font></i></code>
; i.e. elements of
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>B</mi>
</mrow></math>
.
<br/>
<br/>
<b><big><a name="Base Type" id="Base Type">Base Type</a></big></b>
<br/>
If
<code><i><font color="black"><span style='white-space: nowrap'>x</span></font></i></code>
is an
<code><font color="blue"><span style='white-space: nowrap'>AD<</span></font><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i><font color="blue"><span style='white-space: nowrap'>></span></font></code>
object,
<code><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i></code>
is referred to as the base type for
<code><i><font color="black"><span style='white-space: nowrap'>x</span></font></i></code>
.
<br/>
<br/>
<b><big><a name="Elementary Vector" id="Elementary Vector">Elementary Vector</a></big></b>
<br/>
The <code><i>j</i></code>-th elementary vector
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<msup><mi mathvariant='italic'>e</mi>
<mi mathvariant='italic'>j</mi>
</msup>
<mo stretchy="false">∈</mo>
<msup><mi mathvariant='italic'>B</mi>
<mi mathvariant='italic'>m</mi>
</msup>
</mrow></math>
is defined by
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow>
<msubsup><mi mathvariant='italic'>e</mi>
<mi mathvariant='italic'>i</mi>
<mi mathvariant='italic'>j</mi>
</msubsup>
<mo stretchy="false">=</mo>
<mrow><mo stretchy="true">{</mo><mrow><mtable rowalign="center" ><mtr><mtd columnalign="left" >
<mn>1</mn>
</mtd><mtd columnalign="left" >
<mrow><mstyle mathvariant='normal'><mi mathvariant='normal'>if</mi>
</mstyle></mrow>
<mspace width='.3em'/>
<mi mathvariant='italic'>i</mi>
<mo stretchy="false">=</mo>
<mi mathvariant='italic'>j</mi>
</mtd></mtr><mtr><mtd columnalign="left" >
<mn>0</mn>
</mtd><mtd columnalign="left" >
<mrow><mstyle mathvariant='normal'><mi mathvariant='normal'>otherwise</mi>
</mstyle></mrow>
</mtd></mtr></mtable>
</mrow><mo stretchy="true"> </mo></mrow>
</mrow></math>
<br/>
<b><big><a name="Operation" id="Operation">Operation</a></big></b>
<br/>
<br/>
<b><a name="Operation.Atomic" id="Operation.Atomic">Atomic</a></b>
<br/>
An atomic
<code><i><font color="black"><span style='white-space: nowrap'>Type</span></font></i></code>
operation is an operation that
has a
<code><i><font color="black"><span style='white-space: nowrap'>Type</span></font></i></code>
result and is not made up of other
more basic operations.
<br/>
<br/>
<b><a name="Operation.Sequence" id="Operation.Sequence">Sequence</a></b>
<br/>
A sequence of atomic
<code><i><font color="black"><span style='white-space: nowrap'>Type</span></font></i></code>
operations
is called a
<code><i><font color="black"><span style='white-space: nowrap'>Type</span></font></i></code>
operation sequence.
A sequence of atomic <a href="glossary.xml#AD of Base" target="_top"><span style='white-space: nowrap'>AD of Base</span></a>
operations
is referred to as an AD of
<code><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i></code>
operation sequence.
The abbreviated notation AD operation sequence is often used
when it is not necessary to specify the base type.
<br/>
<br/>
<b><a name="Operation.Dependent" id="Operation.Dependent">Dependent</a></b>
<br/>
Suppose that
<code><i><font color="black"><span style='white-space: nowrap'>x</span></font></i></code>
and
<code><i><font color="black"><span style='white-space: nowrap'>y</span></font></i></code>
are
<code><i><font color="black"><span style='white-space: nowrap'>Type</span></font></i></code>
objects and
the result of
<code><font color="blue"><span style='white-space: nowrap'><br/>
     </span></font><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'> < </span></font><i><font color="black"><span style='white-space: nowrap'>y</span></font></i><font color="blue"><span style='white-space: nowrap'><br/>
</span></font></code>
has type <code><font color="blue">bool</font></code> (where
<code><i><font color="black"><span style='white-space: nowrap'>Type</span></font></i></code>
is not the same as <code><font color="blue">bool</font></code>).
If one executes the following code
<code><font color="blue"><span style='white-space: nowrap'><br/>
     if( </span></font><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'> < </span></font><i><font color="black"><span style='white-space: nowrap'>y</span></font></i><font color="blue"><span style='white-space: nowrap'> )<br/>
          </span></font><i><font color="black"><span style='white-space: nowrap'>y</span></font></i><font color="blue"><span style='white-space: nowrap'> = cos(</span></font><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'>);<br/>
     else </span></font><i><font color="black"><span style='white-space: nowrap'>y</span></font></i><font color="blue"><span style='white-space: nowrap'> = sin(</span></font><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'>); <br/>
</span></font></code>
the choice above depends on the value of
<code><i><font color="black"><span style='white-space: nowrap'>x</span></font></i></code>
and
<code><i><font color="black"><span style='white-space: nowrap'>y</span></font></i></code>
and the two choices result in a different
<code><i><font color="black"><span style='white-space: nowrap'>Type</span></font></i></code>
operation sequence.
In this case, we say that the
<code><i><font color="black"><span style='white-space: nowrap'>Type</span></font></i></code>
operation sequence depends
on
<code><i><font color="black"><span style='white-space: nowrap'>x</span></font></i></code>
and
<code><i><font color="black"><span style='white-space: nowrap'>y</span></font></i></code>
.
<br/>
<br/>
<b><a name="Operation.Independent" id="Operation.Independent">Independent</a></b>
<br/>
Suppose that
<code><i><font color="black"><span style='white-space: nowrap'>i</span></font></i></code>
and
<code><i><font color="black"><span style='white-space: nowrap'>n</span></font></i></code>
are <code><font color="blue">size_t</font></code> objects,
and
<code><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'>[</span></font><i><font color="black"><span style='white-space: nowrap'>i</span></font></i><font color="blue"><span style='white-space: nowrap'>]</span></font></code>
,
<code><i><font color="black"><span style='white-space: nowrap'>y</span></font></i></code>
are
<code><i><font color="black"><span style='white-space: nowrap'>Type</span></font></i></code>
objects,
where
<code><i><font color="black"><span style='white-space: nowrap'>Type</span></font></i></code>
is different from <code><font color="blue">size_t</font></code>.
The
<code><i><font color="black"><span style='white-space: nowrap'>Type</span></font></i></code>
sequence of operations corresponding to
<code><font color="blue"><span style='white-space: nowrap'><br/>
     </span></font><i><font color="black"><span style='white-space: nowrap'>y</span></font></i><font color="blue"><span style='white-space: nowrap'> = </span></font><i><font color="black"><span style='white-space: nowrap'>Type</span></font></i><font color="blue"><span style='white-space: nowrap'>(0);<br/>
     for(</span></font><i><font color="black"><span style='white-space: nowrap'>i</span></font></i><font color="blue"><span style='white-space: nowrap'> = 0; </span></font><i><font color="black"><span style='white-space: nowrap'>i</span></font></i><font color="blue"><span style='white-space: nowrap'> < </span></font><i><font color="black"><span style='white-space: nowrap'>n</span></font></i><font color="blue"><span style='white-space: nowrap'>; </span></font><i><font color="black"><span style='white-space: nowrap'>i</span></font></i><font color="blue"><span style='white-space: nowrap'>++)<br/>
          </span></font><i><font color="black"><span style='white-space: nowrap'>y</span></font></i><font color="blue"><span style='white-space: nowrap'> += </span></font><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'>[</span></font><i><font color="black"><span style='white-space: nowrap'>i</span></font></i><font color="blue"><span style='white-space: nowrap'>];<br/>
</span></font></code>
does not depend on the value of
<code><i><font color="black"><span style='white-space: nowrap'>x</span></font></i></code>
or
<code><i><font color="black"><span style='white-space: nowrap'>y</span></font></i></code>
.
In this case, we say that the
<code><i><font color="black"><span style='white-space: nowrap'>Type</span></font></i></code>
operation sequence
is independent of
<code><i><font color="black"><span style='white-space: nowrap'>y</span></font></i></code>
and the elements of
<code><i><font color="black"><span style='white-space: nowrap'>x</span></font></i></code>
.
<br/>
<br/>
<b><big><a name="Parameter" id="Parameter">Parameter</a></big></b>
<br/>
All
<code><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i></code>
objects are parameters.
An
<code><font color="blue"><span style='white-space: nowrap'>AD<</span></font><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i><font color="blue"><span style='white-space: nowrap'>></span></font></code>
object
<code><i><font color="black"><span style='white-space: nowrap'>u</span></font></i></code>
is currently a parameter if
its value does not depend on the value of
an <a href="independent.xml" target="_top"><span style='white-space: nowrap'>Independent</span></a>
variable vector for an
<a href="glossary.xml#Tape.Active" target="_top"><span style='white-space: nowrap'>active tape</span></a>
.
If
<code><i><font color="black"><span style='white-space: nowrap'>u</span></font></i></code>
is a parameter, the function
<a href="parvar.xml" target="_top"><span style='white-space: nowrap'>Parameter(u)</span></a>
returns true
and <a href="parvar.xml" target="_top"><span style='white-space: nowrap'>Variable(u)</span></a>
returns false.
<br/>
<br/>
<b><big><a name="Sparsity Pattern" id="Sparsity Pattern">Sparsity Pattern</a></big></b>
<br/>
CppAD describes a sparse matrix as a vector of sets with each
vector component corresponding to a row
and the elements of the set corresponding to the possibly non-zero columns.
A vector of <code><font color="blue">bool</font></code>
can represent a vector of sets using one bit per element.
(Some vectors of <code><font color="blue">bool</font></code> use one byte per element but
<a href="cppad_vector.xml#vectorBool" target="_top"><span style='white-space: nowrap'>vectorBool</span></a>
is an example class that
uses one bit per element.)
The problem is that this representation uses one bit for both the elements
that are there and the ones that are not.
<code><span style='white-space: nowrap'><br/>
<br/>
</span></code>A vector of <code><font color="blue">std::set<size_t></font></code> does not
represent the elements that are not present,
but it uses about three <code><font color="blue">size_t</font></code> values
for each element that is present.
For example, if <code><font color="blue">size_t</font></code> uses 32 bits,
a vector of <code><font color="blue">std::set<size_t></font></code> uses
about 100 bits for each element that is present in the
vector of sets.
Thus, a vector of <code><font color="blue">std::set<size_t></font></code> should be more efficient for
very sparse matrix representations.
<br/>
<br/>
<b><a name="Sparsity Pattern.Vector of Boolean" id="Sparsity Pattern.Vector of Boolean">Vector of Boolean</a></b>
<br/>
Given a matrix
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>A</mi>
<mo stretchy="false">∈</mo>
<msup><mi mathvariant='italic'>B</mi>
<mrow><mi mathvariant='italic'>m</mi>
<mo stretchy="false">×</mo>
<mi mathvariant='italic'>n</mi>
</mrow>
</msup>
</mrow></math>
,
a vector of <code><font color="blue">bool</font></code>
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>B</mi>
</mrow></math>
of length
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>m</mi>
<mo stretchy="false">×</mo>
<mi mathvariant='italic'>n</mi>
</mrow></math>
is a sparsity pattern for
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>A</mi>
</mrow></math>
if
for
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>i</mi>
<mo stretchy="false">=</mo>
<mn>0</mn>
<mo stretchy="false">,</mo>
<mo stretchy="false">…</mo>
<mo stretchy="false">,</mo>
<mi mathvariant='italic'>m</mi>
<mn>-1</mn>
</mrow></math>
and
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>j</mi>
<mo stretchy="false">=</mo>
<mn>0</mn>
<mo stretchy="false">,</mo>
<mo stretchy="false">…</mo>
<mi mathvariant='italic'>n</mi>
<mn>-1</mn>
</mrow></math>
,
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow>
<msub><mi mathvariant='italic'>A</mi>
<mrow><mi mathvariant='italic'>i</mi>
<mo stretchy="false">,</mo>
<mi mathvariant='italic'>j</mi>
</mrow>
</msub>
<mo stretchy="false">≠</mo>
<mn>0</mn>
<mspace width='.3em'/>
<mo stretchy="false">⇒</mo>
<mspace width='.3em'/>
<msub><mi mathvariant='italic'>B</mi>
<mrow><mi mathvariant='italic'>i</mi>
<mo stretchy="false">*</mo>
<mi mathvariant='italic'>n</mi>
<mo stretchy="false">+</mo>
<mi mathvariant='italic'>j</mi>
</mrow>
</msub>
<mo stretchy="false">=</mo>
<mrow><mstyle mathvariant='normal'><mi mathvariant='normal'>true</mi>
</mstyle></mrow>
</mrow></math>
Given two sparsity patterns
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>B</mi>
</mrow></math>
and
<code><i><font color="black"><span style='white-space: nowrap'>C</span></font></i></code>
for a matrix
<code><i><font color="black"><span style='white-space: nowrap'>A</span></font></i></code>
, we say that
<code><i><font color="black"><span style='white-space: nowrap'>B</span></font></i></code>
is more efficient than
<code><i><font color="black"><span style='white-space: nowrap'>C</span></font></i></code>
if
<code><i><font color="black"><span style='white-space: nowrap'>B</span></font></i></code>
has fewer true elements than
<code><i><font color="black"><span style='white-space: nowrap'>C</span></font></i></code>
.
For example, if
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>A</mi>
</mrow></math>
is the identity matrix,
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow>
<msub><mi mathvariant='italic'>B</mi>
<mrow><mi mathvariant='italic'>i</mi>
<mo stretchy="false">*</mo>
<mi mathvariant='italic'>n</mi>
<mo stretchy="false">+</mo>
<mi mathvariant='italic'>j</mi>
</mrow>
</msub>
<mo stretchy="false">=</mo>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>i</mi>
<mo stretchy="false">=</mo>
<mi mathvariant='italic'>j</mi>
<mo stretchy="false">)</mo>
</mrow></math>
defines an efficient sparsity pattern for
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>A</mi>
</mrow></math>
.
<br/>
<br/>
<b><a name="Sparsity Pattern.Vector of Sets" id="Sparsity Pattern.Vector of Sets">Vector of Sets</a></b>
<br/>
Given a matrix
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>A</mi>
<mo stretchy="false">∈</mo>
<msup><mi mathvariant='italic'>B</mi>
<mrow><mi mathvariant='italic'>m</mi>
<mo stretchy="false">×</mo>
<mi mathvariant='italic'>n</mi>
</mrow>
</msup>
</mrow></math>
,
a vector of sets
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>S</mi>
</mrow></math>
of length
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>m</mi>
</mrow></math>
is a
sparsity pattern for
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>A</mi>
</mrow></math>
if
for
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>i</mi>
<mo stretchy="false">=</mo>
<mn>0</mn>
<mo stretchy="false">,</mo>
<mo stretchy="false">…</mo>
<mo stretchy="false">,</mo>
<mi mathvariant='italic'>m</mi>
<mn>-1</mn>
</mrow></math>
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow>
<msub><mi mathvariant='italic'>A</mi>
<mrow><mi mathvariant='italic'>i</mi>
<mo stretchy="false">,</mo>
<mi mathvariant='italic'>j</mi>
</mrow>
</msub>
<mo stretchy="false">≠</mo>
<mn>0</mn>
<mspace width='.3em'/>
<mo stretchy="false">⇒</mo>
<mspace width='.3em'/>
<mi mathvariant='italic'>j</mi>
<mo stretchy="false">∈</mo>
<msub><mi mathvariant='italic'>S</mi>
<mi mathvariant='italic'>i</mi>
</msub>
</mrow></math>
Given two sparsity patterns
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>S</mi>
</mrow></math>
and
<code><i><font color="black"><span style='white-space: nowrap'>T</span></font></i></code>
for a matrix
<code><i><font color="black"><span style='white-space: nowrap'>A</span></font></i></code>
, we say that
<code><i><font color="black"><span style='white-space: nowrap'>S</span></font></i></code>
is more efficient than
<code><i><font color="black"><span style='white-space: nowrap'>T</span></font></i></code>
if
<code><i><font color="black"><span style='white-space: nowrap'>S</span></font></i></code>
has fewer elements than
<code><i><font color="black"><span style='white-space: nowrap'>T</span></font></i></code>
.
For example, if
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>A</mi>
</mrow></math>
is the identity matrix,
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow>
<msub><mi mathvariant='italic'>S</mi>
<mi mathvariant='italic'>i</mi>
</msub>
<mo stretchy="false">=</mo>
<mo stretchy="false">{</mo>
<mi mathvariant='italic'>i</mi>
<mo stretchy="false">}</mo>
</mrow></math>
defines an efficient sparsity pattern for
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>A</mi>
</mrow></math>
.
<br/>
<br/>
<b><big><a name="Tape" id="Tape">Tape</a></big></b>
<br/>
<br/>
<b><a name="Tape.Active" id="Tape.Active">Active</a></b>
<br/>
A new tape is created and becomes active
after each call of the form (see <a href="independent.xml" target="_top"><span style='white-space: nowrap'>Independent</span></a>
)
<code><font color="blue"><span style='white-space: nowrap'><br/>
     Independent(</span></font><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'>)<br/>
</span></font></code>
All operations that depend on the elements of
<code><i><font color="black"><span style='white-space: nowrap'>x</span></font></i></code>
are
recorded on this active tape.
<br/>
<br/>
<b><a name="Tape.Inactive" id="Tape.Inactive">Inactive</a></b>
<br/>
The
<a href="glossary.xml#Operation.Sequence" target="_top"><span style='white-space: nowrap'>operation sequence</span></a>
stored in a tape must be transferred to a function object using the syntax
(see <a href="funconstruct.xml" target="_top"><span style='white-space: nowrap'>ADFun<Base> f(x, y)</span></a>
)
<code><font color="blue"><span style='white-space: nowrap'><br/>
     ADFun<</span></font><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i><font color="blue"><span style='white-space: nowrap'>> </span></font><i><font color="black"><span style='white-space: nowrap'>f</span></font></i><font color="blue"><span style='white-space: nowrap'>( </span></font><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'>, </span></font><i><font color="black"><span style='white-space: nowrap'>y</span></font></i><font color="blue"><span style='white-space: nowrap'>)<br/>
</span></font></code>
or using the syntax (see <a href="dependent.xml" target="_top"><span style='white-space: nowrap'>f.Dependent(x, y)</span></a>
)
<code><font color="blue"><span style='white-space: nowrap'><br/>
     </span></font><i><font color="black"><span style='white-space: nowrap'>f</span></font></i><font color="blue"><span style='white-space: nowrap'>.Dependent( </span></font><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'>, </span></font><i><font color="black"><span style='white-space: nowrap'>y</span></font></i><font color="blue"><span style='white-space: nowrap'>)<br/>
</span></font></code>
After such a transfer, the tape becomes inactive.
<br/>
<br/>
<b><a name="Tape.Independent Variable" id="Tape.Independent Variable">Independent Variable</a></b>
<br/>
While the tape is active, we refer to the elements of
<code><i><font color="black"><span style='white-space: nowrap'>x</span></font></i></code>
as the independent variables for the tape.
When the tape becomes inactive,
the corresponding objects become
<a href="glossary.xml#Parameter" target="_top"><span style='white-space: nowrap'>parameters</span></a>
.
<br/>
<br/>
<b><a name="Tape.Dependent Variables" id="Tape.Dependent Variables">Dependent Variables</a></b>
<br/>
While the tape is active, we use the term dependent variables for the tape
for any objects whose value depends on the independent variables for the tape.
When the tape becomes inactive,
the corresponding objects become
<a href="glossary.xml#Parameter" target="_top"><span style='white-space: nowrap'>parameters</span></a>
.
<br/>
<br/>
<b><big><a name="Taylor Coefficient" id="Taylor Coefficient">Taylor Coefficient</a></big></b>
<br/>
Suppose
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>X</mi>
<mo stretchy="false">:</mo>
<mi mathvariant='italic'>B</mi>
<mo stretchy="false">→</mo>
<msup><mi mathvariant='italic'>B</mi>
<mi mathvariant='italic'>n</mi>
</msup>
</mrow></math>
is a
is
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>p</mi>
</mrow></math>
times continuously differentiable function
in some neighborhood of zero.
For
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>k</mi>
<mo stretchy="false">=</mo>
<mn>0</mn>
<mo stretchy="false">,</mo>
<mo stretchy="false">…</mo>
<mo stretchy="false">,</mo>
<mi mathvariant='italic'>p</mi>
</mrow></math>
,
we use the column vector
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<msup><mi mathvariant='italic'>x</mi>
<mrow><mo stretchy="false">(</mo>
<mi mathvariant='italic'>k</mi>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mo stretchy="false">∈</mo>
<msup><mi mathvariant='italic'>B</mi>
<mi mathvariant='italic'>n</mi>
</msup>
</mrow></math>
for the <code><i>k</i></code>-th order
Taylor coefficient corresponding to
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>X</mi>
</mrow></math>
which is defined by
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow>
<msup><mi mathvariant='italic'>x</mi>
<mrow><mo stretchy="false">(</mo>
<mi mathvariant='italic'>k</mi>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mo stretchy="false">=</mo>
<mfrac><mrow><mn>1</mn>
</mrow>
<mrow><mi mathvariant='italic'>k</mi>
<mo stretchy="false">!</mo>
</mrow>
</mfrac>
<mfrac><mrow><msup><mo stretchy="false">∂</mo>
<mrow><mi mathvariant='italic'>k</mi>
</mrow>
</msup>
</mrow>
<mrow><mo stretchy="false">∂</mo>
<msup><mrow><mi mathvariant='italic'>t</mi>
</mrow>
<mrow><mi mathvariant='italic'>k</mi>
</mrow>
</msup>
</mrow>
</mfrac>
<mi mathvariant='italic'>X</mi>
<mo stretchy="false">(</mo>
<mn>0</mn>
<mo stretchy="false">)</mo>
</mrow></math>
It follows that
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow>
<mi mathvariant='italic'>X</mi>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
<mo stretchy="false">=</mo>
<msup><mi mathvariant='italic'>x</mi>
<mrow><mo stretchy="false">(</mo>
<mn>0</mn>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mo stretchy="false">+</mo>
<msup><mi mathvariant='italic'>x</mi>
<mrow><mo stretchy="false">(</mo>
<mn>1</mn>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">+</mo>
<mo stretchy="false">⋯</mo>
<mo stretchy="false">+</mo>
<msup><mi mathvariant='italic'>x</mi>
<mrow><mo stretchy="false">(</mo>
<mi mathvariant='italic'>p</mi>
<mo stretchy="false">)</mo>
</mrow>
</msup>
<msup><mi mathvariant='italic'>t</mi>
<mi mathvariant='italic'>p</mi>
</msup>
<mo stretchy="false">+</mo>
<mi mathvariant='italic'>R</mi>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
</mrow></math>
where the remainder
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>R</mi>
<mo stretchy="false">(</mo>
<mi mathvariant='italic'>t</mi>
<mo stretchy="false">)</mo>
</mrow></math>
divided by
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<msup><mi mathvariant='italic'>t</mi>
<mi mathvariant='italic'>p</mi>
</msup>
</mrow></math>
converges to zero and
<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow>
<mi mathvariant='italic'>t</mi>
</mrow></math>
goes to zero.
<br/>
<br/>
<b><big><a name="Variable" id="Variable">Variable</a></big></b>
<br/>
An
<code><font color="blue"><span style='white-space: nowrap'>AD<</span></font><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i><font color="blue"><span style='white-space: nowrap'>></span></font></code>
object
<code><i><font color="black"><span style='white-space: nowrap'>u</span></font></i></code>
is a variable if
its value depends on an independent variable vector for
a currently <a href="glossary.xml#Tape.Active" target="_top"><span style='white-space: nowrap'>active tape</span></a>
.
If
<code><i><font color="black"><span style='white-space: nowrap'>u</span></font></i></code>
is a variable,
<a href="parvar.xml" target="_top"><span style='white-space: nowrap'>Variable(u)</span></a>
returns true and
<a href="parvar.xml" target="_top"><span style='white-space: nowrap'>Parameter(u)</span></a>
returns false.
For example,
directly after the code sequence
<code><font color="blue"><span style='white-space: nowrap'><br/>
     Independent(</span></font><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'>);<br/>
     AD<double> </span></font><i><font color="black"><span style='white-space: nowrap'>u</span></font></i><font color="blue"><span style='white-space: nowrap'> = </span></font><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'>[0];<br/>
</span></font></code>
the
<code><font color="blue"><span style='white-space: nowrap'>AD<double></span></font></code>
object
<code><i><font color="black"><span style='white-space: nowrap'>u</span></font></i></code>
is currently a variable.
Directly after the code sequence
<code><font color="blue"><span style='white-space: nowrap'><br/>
     Independent(</span></font><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'>);<br/>
     AD<double> </span></font><i><font color="black"><span style='white-space: nowrap'>u</span></font></i><font color="blue"><span style='white-space: nowrap'> = </span></font><i><font color="black"><span style='white-space: nowrap'>x</span></font></i><font color="blue"><span style='white-space: nowrap'>[0];<br/>
     </span></font><i><font color="black"><span style='white-space: nowrap'>u</span></font></i><font color="blue"><span style='white-space: nowrap'> = 5;<br/>
</span></font></code>
<code><i><font color="black"><span style='white-space: nowrap'>u</span></font></i></code>
is currently a <a href="glossary.xml#Parameter" target="_top"><span style='white-space: nowrap'>parameter</span></a>
(not a variable).
<code><span style='white-space: nowrap'><br/>
<br/>
</span></code>Note that we often drop the word currently and
just refer to an
<code><font color="blue"><span style='white-space: nowrap'>AD<</span></font><i><font color="black"><span style='white-space: nowrap'>Base</span></font></i><font color="blue"><span style='white-space: nowrap'>></span></font></code>
object as a variable
or parameter.
<hr/>Input File: omh/glossary.omh
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