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## 1Purpose

g01ea is the AD Library version of the primal routine g01eaf. Based (in the C++ interface) on overload resolution, g01ea can be used for primal, tangent and adjoint evaluation. It supports tangents and adjoints of first order.

## 2Specification

Fortran Interface
 Subroutine g01ea_AD_f ( tail, x, p, ifail)
 Integer, Intent (Inout) :: ifail ADTYPE, Intent (In) :: x ADTYPE, Intent (Out) :: p Character (1), Intent (In) :: tail Type (c_ptr), Intent (Inout) :: ad_handle
Corresponding to the overloaded C++ function, the Fortran interface provides five routines with names reflecting the type used for active real arguments. The actual subroutine and type names are formed by replacing AD and ADTYPE in the above as follows:
C++ Interface
#include <dco.hpp>
namespace nag {
}
}
The function is overloaded on ADTYPE which represents the type of active arguments. ADTYPE may be any of the following types:
double,
dco::ga1s<double>::type,
dco::gt1s<double>::type

## 3Description

g01ea is the AD Library version of the primal routine g01eaf.
g01eaf returns a one or two tail probability for the standard Normal distribution. For further information see Section 3 in the documentation for g01eaf.

## 4References

NIST Digital Library of Mathematical Functions
Hastings N A J and Peacock J B (1975) Statistical Distributions Butterworth

## 5Arguments

In addition to the arguments present in the interface of the primal routine, g01ea includes some arguments specific to AD.
A brief summary of the AD specific arguments is given below. For the remainder, links are provided to the corresponding argument from the primal routine. A tooltip popup for all arguments can be found by hovering over the argument name in Section 2 and in this section.
Note that the primal routine is a function whereas g01ea_a1w_f, is a subroutine, where the function value is returned in the additional output parameter, p.
On entry: a configuration object that holds information on the differentiation strategy. Details on setting the AD strategy are described in AD handle object in the NAG AD Library Introduction.
2: tail – character Input
3: Input
On exit: a one or two tail probability for the standard Normal distribution.
5: ifail – Integer Input/Output

## 6Error Indicators and Warnings

g01ea preserves all error codes from g01eaf and in addition can return:
${\mathbf{ifail}}=-89$
See Error Handling in the NAG AD Library Introduction for further information.
${\mathbf{ifail}}=-199$
The routine was called using a strategy that has not yet been implemented.
See AD Strategies in the NAG AD Library Introduction for further information.
${\mathbf{ifail}}=-444$
A C++ exception was thrown.
The error message will show the details of the C++ exception text.
${\mathbf{ifail}}=-899$
Dynamic memory allocation failed for AD.
See Error Handling in the NAG AD Library Introduction for further information.

Not applicable.

## 8Parallelism and Performance

g01ea is not threaded in any implementation.

None.

## 10Example

The following examples are variants of the example for g01eaf, modified to demonstrate calling the NAG AD Library.
Description of the primal example.
Four values of tail and x are input and the probabilities calculated and printed.

Language Source File Data Results
Fortran g01ea_a1w_fe.f90 g01ea_a1w_fe.d g01ea_a1w_fe.r
C++ g01ea_a1w_hcppe.cpp g01ea_a1w_hcppe.d g01ea_a1w_hcppe.r

### 10.2Tangent modes

Language Source File Data Results
Fortran g01ea_t1w_fe.f90 g01ea_t1w_fe.d g01ea_t1w_fe.r
C++ g01ea_t1w_hcppe.cpp g01ea_t1w_hcppe.d g01ea_t1w_hcppe.r

### 10.3Passive mode

Language Source File Data Results
Fortran g01ea_p0w_fe.f90 g01ea_p0w_fe.d g01ea_p0w_fe.r
C++ g01ea_p0w_hcppe.cpp g01ea_p0w_hcppe.d g01ea_p0w_hcppe.r