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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-ddot@esm/index.mjs';Calculates the dot product of two double-precision floating-point vectors x and y.
import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@esm/index.mjs';
import array from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-array@esm/index.mjs';
var x = array( new Float64Array( [ 4.0, 2.0, -3.0, 5.0, -1.0 ] ) );
var y = array( new Float64Array( [ 2.0, 6.0, -1.0, -4.0, 8.0 ] ) );
var z = ddot( x, y );
// returns <ndarray>
var v = z.get();
// returns -5.0The function has the following parameters:
- x: a non-zero-dimensional
ndarraywhose underlying data type isfloat64. Must be broadcast-compatible withy. - y: a non-zero-dimensional
ndarraywhose underlying data type isfloat64. Must be broadcast-compatible withx. - dim: dimension for which to compute the dot product. Must be a negative integer. Negative indices are resolved relative to the last array dimension, with the last dimension corresponding to
-1. Default:-1.
If provided at least one input ndarray having more than one dimension, the input ndarrays are broadcasted to a common shape. For multi-dimensional input ndarrays, the function performs batched computation, such that the function computes the dot product for each pair of vectors in x and y according to the specified dimension index.
import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@esm/index.mjs';
import array from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-array@esm/index.mjs';
var opts = {
'shape': [ 2, 3 ]
};
var x = array( new Float64Array( [ 4.0, 2.0, -3.0, 5.0, -1.0, 3.0 ] ), opts );
var y = array( new Float64Array( [ 2.0, 6.0, -1.0, -4.0, 8.0, 2.0 ] ), opts );
var z = ddot( x, y );
// returns <ndarray>
var v1 = z.get( 0 );
// returns 23.0
var v2 = z.get( 1 );
// returns -22.0- The size of the contracted dimension must be the same for both input
ndarrays. - The function resolves the dimension index for which to compute the dot product before broadcasting.
- Negative indices are resolved relative to the last
ndarraydimension, with the last dimension corresponding to-1. - The output
ndarrayhas the same data type as the inputndarraysand has a shape which is determined by broadcasting and excludes the contracted dimension. - If provided empty vectors, the dot product is
0. ddot()provides a higher-level interface to the BLAS level 1 functionddot.
<!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 ndarray2array from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-to-array@esm/index.mjs';
import array from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-array@esm/index.mjs';
import ddot from 'https://cdn.jsdelivr.net/gh/stdlib-js/blas-ddot@esm/index.mjs';
var opts = {
'dtype': 'float64'
};
var x = array( discreteUniform( 10, 0, 100, opts ), {
'shape': [ 5, 2 ]
});
console.log( ndarray2array( x ) );
var y = array( discreteUniform( 10, 0, 10, opts ), {
'shape': x.shape
});
console.log( ndarray2array( y ) );
var z = ddot( x, y, -1 );
console.log( ndarray2array( z ) );
</script>
</body>
</html>@stdlib/blas-base/ddot: calculate the dot product of two double-precision floating-point vectors.@stdlib/blas-gdot: calculate the dot product of two vectors.@stdlib/blas-sdot: calculate the dot product of two single-precision floating-point vectors.
This package is part of stdlib, a standard library with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.
See LICENSE.
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