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# dcusumkbn2

> Compute the cumulative sum of a one-dimensional double-precision floating-point ndarray using a second-order iterative Kahan–Babuška algorithm.

<section class="intro">

</section>

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<section class="usage">

## Usage

```javascript
var dcusumkbn2 = require( '@stdlib/blas/ext/base/ndarray/dcusumkbn2' );
```

#### dcusumkbn2( arrays )

Computes the cumulative sum of a one-dimensional double-precision floating-point ndarray using a second-order iterative Kahan–Babuška algorithm.

```javascript
var Float64Vector = require( '@stdlib/ndarray/vector/float64' );
var scalar2ndarray = require( '@stdlib/ndarray/from-scalar' );

var x = new Float64Vector( [ 1.0, 3.0, 4.0, 2.0 ] );
var y = new Float64Vector( [ 0.0, 0.0, 0.0, 0.0 ] );

var initial = scalar2ndarray( 0.0, {
    'dtype': 'float64'
});

var z = dcusumkbn2( [ x, y, initial ] );
// returns <ndarray>[ 1.0, 4.0, 8.0, 10.0 ]

var bool = ( z === y );
// returns true
```

The function has the following parameters:

-   **arrays**: array-like object containing the following ndarrays:

    -   a one-dimensional input ndarray.
    -   a one-dimensional output ndarray.
    -   a zero-dimensional ndarray containing the initial sum.

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<section class="notes">

## Notes

-   If provided an empty one-dimensional input ndarray, the function returns the output ndarray unchanged.

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<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var discreteUniform = require( '@stdlib/random/discrete-uniform' );
var zerosLike = require( '@stdlib/ndarray/zeros-like' );
var scalar2ndarray = require( '@stdlib/ndarray/from-scalar' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var dcusumkbn2 = require( '@stdlib/blas/ext/base/ndarray/dcusumkbn2' );

var opts = {
    'dtype': 'float64'
};

var x = discreteUniform( [ 10 ], -50, 50, opts );
console.log( ndarray2array( x ) );

var y = zerosLike( x );
console.log( ndarray2array( y ) );

var initial = scalar2ndarray( 100.0, opts );

var v = dcusumkbn2( [ x, y, initial ] );
console.log( ndarray2array( v ) );
```

</section>

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<section class="references">

## References

-   Klein, Andreas. 2005. "A Generalized Kahan-Babuška-Summation-Algorithm." _Computing_ 76 (3): 279–93. doi:[10.1007/s00607-005-0139-x][@klein:2005a].

</section>

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<section class="links">

[@klein:2005a]: https://doi.org/10.1007/s00607-005-0139-x

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