Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

ID 766686
Date 6/24/2024
Public

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v?ExpInt1

Computes the exponential integral of vector elements.

Syntax

call vsexpint1( n, a, y )

call vsexpint1i(n, a, inca, y, incy)

call vmsexpint1( n, a, y, mode )

call vmsexpint1i(n, a, inca, y, incy, mode)

call vdexpint1( n, a, y )

call vdexpint1i(n, a, inca, y, incy)

call vdexpint1( n, a, y, mode )

call vmdexpint1i(n, a, inca, y, incy, mode)

Include Files

  • mkl_vml.f90

Input Parameters

Name

Type

Description

n

INTEGER, INTENT(IN)

Specifies the number of elements to be calculated.

a

REAL (KIND=4), INTENT(IN) for vsexpint1, vmsexpint1

REAL (KIND=8), INTENT(IN) for vdexpint1, vmdexpint1

Array that specifies the input vector a.

inca, incy

INTEGER, INTENT(IN)

Specifies increments for the elements of a and y.

mode

INTEGER(KIND=8), INTENT(IN)

Overrides global VM mode setting for this function call. See vmlSetMode for possible values and their description.

Output Parameters

Name

Type

Description

y

REAL (KIND=4), INTENT(OUT) for vsexpint1, vmsexpint1

REAL (KIND=8), INTENT(OUT) for vdexpint1, vmdexpint1

Array that specifies the output vector y.

Description

The v?ExpInt1 function computes the exponential integral E1 of vector elements.

For positive real values x, this can be written as:

.

For negative real values x, the result is defined as NAN.

Special Values for Real Function v?ExpInt1(x)
Argument Result VM Error Status Exception
x < +0 QNAN VML_STATUS_ERRDOM INVALID
+0 + VML_STATUS_SING ZERODIVIDE
-0 + VML_STATUS_SING ZERODIVIDE
+ +0    
- QNAN VML_STATUS_ERRDOM INVALID
QNAN QNAN    
SNAN QNAN   INVALID