umuldw

Compute the double word product of two unsigned 32-bit integers.

Usage

var umuldw = require( '@stdlib/math/base/ops/umuldw' );

umuldw( a, b )

Multiplies two unsigned 32-bit integers and returns an array of two unsigned 32-bit integers (in big endian order) which represents the unsigned 64-bit integer product.

var v = umuldw( 1, 10 );
// returns [ 0, 10 ]

v = umuldw( 0x80000000, 0x80000000 ); // 2^31 * 2^31 = 4611686018427388000 => 32-bit integer overflow
// returns [ 1073741824, 0 ]

umuldw.assign( a, b, out, stride, offset )

Multiplies two unsigned 32-bit integers and assigns results representing the unsigned 64-bit integer product (in big endian order) to a provided output array.

var out = [ 0, 0 ];

var v = umuldw.assign( 1, 10, out, 1, 0 );
// returns [ 0, 10 ]

var bool = ( v === out );
// returns true

Notes

When computing the product of 32-bit integer values in double-precision floating-point format (the default JavaScript numeric data type), computing the double word product is necessary in order to avoid exceeding the maximum safe double-precision floating-point integer value.

Examples

var lpad = require( '@stdlib/string/left-pad' );
var umuldw = require( '@stdlib/math/base/ops/umuldw' );

var i;
var j;
var y;

for ( i = 0xFFFFFFF0; i < 0xFFFFFFFF; i++ ) {
    for ( j = i; j < 0xFFFFFFFF; j++) {
        y = umuldw( i, j );
        console.log( '%d x %d = 0x%s%s', i, j, lpad( y[0].toString( 16 ), 8, '0' ), lpad( y[1].toString( 16 ), 8, '0' ) );
    }
}