\(\newcommand{\W}[1]{ \; #1 \; }\) \(\newcommand{\R}[1]{ {\rm #1} }\) \(\newcommand{\B}[1]{ {\bf #1} }\) \(\newcommand{\D}[2]{ \frac{\partial #1}{\partial #2} }\) \(\newcommand{\DD}[3]{ \frac{\partial^2 #1}{\partial #2 \partial #3} }\) \(\newcommand{\Dpow}[2]{ \frac{\partial^{#1}}{\partial {#2}^{#1}} }\) \(\newcommand{\dpow}[2]{ \frac{ {\rm d}^{#1}}{{\rm d}\, {#2}^{#1}} }\)

PrintFor

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Printing AD Values During Forward Mode

Syntax

f . Forward (0, x )

f . Forward (0, x , s )

PrintFor ( before , value )

PrintFor ( notpos , before , value , after )

See Also

ad_output

Purpose

The zero order forward mode command

f . Forward (0, x )

sets the Independent Variable vector equal to x . It then computes a value for all of the dependent variables in the operation sequence corresponding to f . Putting a PrintFor in the operation sequence, prints value , corresponding to x , to be printed during zero order forward operations.

f.Forward(0, x)

The objects f , x , and the purpose for this operation, are documented in Forward .

notpos

If present, the argument notpos has one of the following prototypes

      const AD < Base >& notpos

      const VecAD < Base >:: reference& notpos

In this case the text and value will be printed if and only if notpos is not positive (greater than zero) and a finite number.

before

The argument before has prototype

const char * before

This text is written to std::cout before value .

value

The argument value has one of the following prototypes

      const AD < Base >& value

      const VecAD < Base >:: reference& value

The value , that corresponds to x , is written to std::cout during the execution of

f . Forward (0, x )

Note that value may be a Variable or Parameter . If a parameter is Dynamic its value will depend on the previous call to new_dynamic .

after

The argument after has prototype

const char * after

This text is written to std::cout after value .

s

You can redirect this output to any standard output stream using the syntax

f . Forward (0, x , s )

see s in the zero order forward mode documentation.

Discussion

This is helpful for understanding why tape evaluations have trouble. For example, if one of the operations in f is log ( value ) and value < 0 , the corresponding result will nan .

Example

The program print_for_cout.cpp is an example and test that prints to standard output. The output of this program states the conditions for passing and failing the test. The function print_for_string.cpp is an example and test that prints to an standard string stream. This function automatically check for correct output.