lines 9-141 of file: include/cppad/utility/speed_test.hpp

{xrst_begin speed_test}
{xrst_spell
   ctime
   gettimeofday
}

Run One Speed Test and Return Results
#####################################

Syntax
******

   # ``include <cppad/utility/speed_test.hpp>``

*rate_vec* = ``speed_test`` ( *test* , *size_vec* , *time_min* )

See Also
********
:ref:`time_test-name`

Purpose
*******
The ``speed_test`` function executes a speed test
for various sized problems
and reports the rate of execution.

Motivation
**********
It is important to separate small calculation units
and test them individually.
This way individual changes can be tested in the context of the
routine that they are in.
On many machines, accurate timing of a very short execution
sequences is not possible.
In addition,
there may be set up and tear down time for a test that
we do not really want included in the timing.
For this reason ``speed_test``
automatically determines how many times to
repeat the section of the test that we wish to time.

Include
*******
The file ``cppad/utility/speed_test.hpp`` defines the
``speed_test`` function.
This file is included by ``cppad/cppad.hpp``
and it can also be included separately with out the rest of
the ``CppAD`` routines.

Vector
******
We use *Vector* to denote a
:ref:`simple vector class<SimpleVector-name>` with elements
of type ``size_t`` .

test
****
The ``speed_test`` argument *test* is a function with the syntax

   *test* ( *size* , *repeat* )

and its return value is ``void`` .

size
====
The *test* argument *size* has prototype

   ``size_t`` *size*

It specifies the size for this test.

repeat
======
The *test* argument *repeat* has prototype

   ``size_t`` *repeat*

It specifies the number of times to repeat the test.

size_vec
********
The ``speed_test`` argument *size_vec* has prototype

   ``const`` *Vector* & *size_vec*

This vector determines the size for each of the tests problems.

time_min
********
The argument *time_min* has prototype

   ``double`` *time_min*

It specifies the minimum amount of time in seconds
that the *test* routine should take.
The *repeat* argument to *test* is increased
until this amount of execution time is reached.

rate_vec
********
The return value *rate_vec* has prototype

   *Vector* & *rate_vec*

We use :math:`n` to denote its size which is the same as
the vector *size_vec* .
For :math:`i = 0 , \ldots , n-1`,

   *rate_vec* [ *i* ]

is the ratio of *repeat* divided by time in seconds
for the problem with size *size_vec* [ *i* ] .

Timing
******
If your system supports the unix ``gettimeofday`` function,
it will be used to measure time.
Otherwise,
time is measured by the difference in
::

   (double) clock() / (double) CLOCKS_PER_SEC

in the context of the standard ``<ctime>`` definitions.
{xrst_toc_hidden
   speed/example/speed_test.cpp
}
Example
*******
The routine :ref:`speed_test.cpp-name` is an example and test
of ``speed_test`` .

{xrst_end speed_test}