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Calculate the dot product of two double-precision floating-point vectors.
The dot product (or scalar product) is defined as
import ddot from 'https://cdn.jsdelivr.net/gh/stdlib-js/blas-base-ddot@esm/index.mjs';Calculates the dot product of vectors x and y.
import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@esm/index.mjs';
var x = new Float64Array( [ 4.0, 2.0, -3.0, 5.0, -1.0 ] );
var y = new Float64Array( [ 2.0, 6.0, -1.0, -4.0, 8.0 ] );
var z = ddot( x.length, x, 1, y, 1 );
// returns -5.0The function has the following parameters:
- N: number of indexed elements.
- x: input
Float64Array. - strideX: index increment for
x. - y: input
Float64Array. - strideY: index increment for
y.
The N and strides parameters determine which elements in the strided arrays are accessed at runtime. For example, to calculate the dot product of every other value in x and the first N elements of y in reverse order,
import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@esm/index.mjs';
var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float64Array( [ 1.0, 1.0, 1.0, 1.0, 1.0, 1.0 ] );
var z = ddot( 3, x, 2, y, -1 );
// returns 9.0Note that indexing is relative to the first index. To introduce an offset, use typed array views.
import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@esm/index.mjs';
// Initial arrays...
var x0 = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y0 = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
// Create offset views...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element
var z = ddot( 3, x1, -2, y1, 1 );
// returns 128.0Calculates the dot product of x and y using alternative indexing semantics.
import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@esm/index.mjs';
var x = new Float64Array( [ 4.0, 2.0, -3.0, 5.0, -1.0 ] );
var y = new Float64Array( [ 2.0, 6.0, -1.0, -4.0, 8.0 ] );
var z = ddot.ndarray( x.length, x, 1, 0, y, 1, 0 );
// returns -5.0The function has the following additional parameters:
- offsetX: starting index for
x. - offsetY: starting index for
y.
While typed array views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to calculate the dot product of every other value in x starting from the second value with the last 3 elements in y in reverse order
import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@esm/index.mjs';
var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
var z = ddot.ndarray( 3, x, 2, 1, y, -1, y.length-1 );
// returns 128.0<!DOCTYPE html>
<html lang="en">
<body>
<script type="module">
import discreteUniform from 'https://cdn.jsdelivr.net/gh/stdlib-js/random-array-discrete-uniform@esm/index.mjs';
import ddot from 'https://cdn.jsdelivr.net/gh/stdlib-js/blas-base-ddot@esm/index.mjs';
var opts = {
'dtype': 'float64'
};
var x = discreteUniform( 10, 0, 100, opts );
console.log( x );
var y = discreteUniform( x.length, 0, 10, opts );
console.log( y );
var out = ddot.ndarray( x.length, x, 1, 0, y, -1, y.length-1 );
console.log( out );
</script>
</body>
</html>@stdlib/blas-base/dsdot: calculate the dot product with extended accumulation and result of two single-precision floating-point vectors.@stdlib/blas-base/gdot: calculate the dot product of two vectors.@stdlib/blas-base/sdot: calculate the dot product of two single-precision floating-point vectors.@stdlib/blas-base/sdsdot: calculate the dot product of two single-precision floating-point vectors with extended accumulation.@stdlib/blas-ddot: calculate the dot product of two double-precision floating-point vectors.
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See LICENSE.
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