v?ExpInt1

Developer Reference for Intel® oneAPI Math Kernel Library for C

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ID 766684

Date 4/28/2026

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vsExpInt1 vdExpInt1 vmsExpInt1 vmdExpInt1 Computes the exponential integral of vector elements.

vhExpInt1 ( n , a , y ) ;

vhExpInt1I(n, a, inca, y, incy);

vmhExpInt1 ( n , a , y , mode ) ;

vmhExpInt1I(n, a, inca, y, incy, mode);

vsExpInt1 ( n , a , y ) ;

vsExpInt1I(n, a, inca, y, incy);

vmsExpInt1 ( n , a , y , mode ) ;

vmsExpInt1I(n, a, inca, y, incy, mode);

vdExpInt1 ( n , a , y ) ;

vdExpInt1I(n, a, inca, y, incy);

vmdExpInt1 ( n , a , y , mode ) ;

vmdExpInt1I(n, a, inca, y, incy, mode);

Name	Type	Description
`n`	const MKL_INT	Specifies the number of elements to be calculated.
`a`	const _Float16* for `vhExpInt1` , `vmhExpInt1` const float* for `vsExpInt1` , `vmsExpInt1` const double* for `vdExpInt1` , `vmdExpInt1`	Pointer to an array that contains the input vector `a` .
`inca`, `incy`	const MKL_INT	Specifies increments for the elements of `a` and `y` .
`mode`	const MKL_INT64	Overrides global VM mode setting for this function call. See vmlSetMode (Sets a new mode for VM functions according to the mode parameter and stores the previous VM mode to oldmode.) for possible values and their description.

Name	Type	Description
`y`	_Float16* for `vhExpInt1` , `vmhExpInt1` float* for `vsExpInt1` , `vmsExpInt1` double* for `vdExpInt1` , `vmdExpInt1`	Pointer to an array that contains the output vector `y` .

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