feat: add /blas/ext/base/dnancusumkbn2

Signed-off-by: Shabareesh Shetty <[email protected]>

Author: ShabiShett07

lib/node_modules/@stdlib/blas/ext/base/dnancusumkbn2/lib/ndarray.js

@@ -0,0 +1,108 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2020 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var isnan = require( '@stdlib/math/base/assert/is-nan' );
+var abs = require( '@stdlib/math/base/special/abs' );
+
+
+// MAIN //
+
+/**
+* Computes the cumulative sum of double-precision floating-point strided array elements, ignoring `NaN` values and using a second-order iterative Kahan–Babuška algorithm.
+*
+* ## Method
+*
+* -   This implementation uses a second-order iterative Kahan–Babuška algorithm, as described by Klein (2005).
+*
+* ## References
+*
+* -   Klein, Andreas. 2005. "A Generalized Kahan-Babuška-Summation-Algorithm." _Computing_ 76 (3): 279–93. doi:[10.1007/s00607-005-0139-x](https://doi.org/10.1007/s00607-005-0139-x).
+*
+* @param {PositiveInteger} N - number of indexed elements
+* @param {number} sum - initial sum
+* @param {Float64Array} x - input array
+* @param {integer} strideX - stride length for `x`
+* @param {NonNegativeInteger} offsetX - starting index for `x`
+* @param {Float64Array} y - output array
+* @param {integer} strideY - stride length for `y`
+* @param {NonNegativeInteger} offsetY - starting index for `y`
+* @returns {Float64Array} output array
+*
+* @example
+* var Float64Array = require( '@stdlib/array/float64' );
+*
+* var x = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, NaN ] );
+* var y = new Float64Array( x.length );
+*
+* var v = dnancusumkbn2( 4, 0.0, x, 2, 1, y, 1, 0 );
+* // returns <Float64Array>[ 1.0, -1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0.0 ]
+*/
+function dcusumkbn2( N, sum, x, strideX, offsetX, y, strideY, offsetY ) {
+	var ccs;
+	var ix;
+	var iy;
+	var cs;
+	var cc;
+	var v;
+	var t;
+	var c;
+	var i;
+
+	if ( N <= 0 ) {
+		return y;
+	}
+	ix = offsetX;
+	iy = offsetY;
+
+	ccs = 0.0; // second order correction term for lost low order bits
+  cs = 0.0; // first order correction term for lost low order bits
+	for ( i = 0; i < N; i++ ) {
+		v = x[ ix ];
+    if ( isnan( v ) === false ) {
+   	  t = sum + v;
+		  if ( abs( sum ) >= abs( v ) ) {
+			  c = (sum-t) + v;
+		  } else {
+			  c = (v-t) + sum;
+		  }
+		  sum = t;
+		  t = cs + c;
+		  if ( abs( cs ) >= abs( c ) ) {
+			  cc = (cs-t) + c;
+		  } else {
+			  cc = (c-t) + cs;
+		  }
+		  cs = t;
+		  ccs += cc;
+
+		  y[ iy ] = sum + cs + ccs;
+    }
+		ix += strideX;
+		iy += strideY;
+	}
+	return y;
+}
+
+
+// EXPORTS //
+
+module.exports = dnancusumkbn2;