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dlaset

Set the off-diagonal elements and the diagonal elements of a double-precision floating-point matrix to specified values.

Usage

var dlaset = require( '@stdlib/lapack/base/dlaset' );

dlaset( order, uplo, M, N, alpha, beta, A, LDA )

Sets the off-diagonal elements and the diagonal elements of a double-precision floating-point matrix to specified values.

var Float64Array = require( '@stdlib/array/float64' );

var A = new Float64Array( 4 );

dlaset( 'row-major', 'all', 2, 2, 2.0, 1.0, A, 2 );
// A => <Float64Array>[ 1.0, 2.0, 2.0, 1.0 ]

The function has the following parameters:

  • order: storage layout.
  • uplo: specifies whether to set the upper or lower triangular/trapezoidal part of a matrix A.
  • M: number of rows in A.
  • N: number of columns in A.
  • alpha: value assigned to off-diagonal elements.
  • beta: value assigned to diagonal elements.
  • A: input Float64Array.
  • LDA: stride of the first dimension of A (a.k.a., leading dimension of the matrix A).

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

var Float64Array = require( '@stdlib/array/float64' );

// Initial array:
var A0 = new Float64Array( 5 );

// Create offset view:
var A1 = new Float64Array( A0.buffer, A0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

dlaset( 'row-major', 'all', 2, 2, 2.0, 1.0, A1, 2 );
// A0 => <Float64Array>[ 0.0, 1.0, 2.0, 2.0, 1.0 ]

dlaset.ndarray( uplo, M, N, alpha, beta, A, sa1, sa2, oa )

Sets the off-diagonal elements and the diagonal elements of a double-precision floating-point matrix to specified values using alternative indexing semantics.

var Float64Array = require( '@stdlib/array/float64' );

var A = new Float64Array( 4 );

dlaset.ndarray( 'all', 2, 2, 2.0, 1.0, A, 2, 1, 0 );
// A => <Float64Array>[ 1.0, 2.0, 2.0, 1.0 ]

The function has the following parameters:

  • uplo: specifies whether to set the upper or lower triangular/trapezoidal part of a matrix A.
  • M: number of rows in A.
  • N: number of columns in A.
  • alpha: value assigned to off-diagonal elements.
  • beta: value assigned to diagonal elements.
  • A: input Float64Array.
  • sa1: stride of the first dimension of A.
  • sa2: stride of the second dimension of A.
  • oa: starting index for A.

While typed array views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example,

var Float64Array = require( '@stdlib/array/float64' );

var A = new Float64Array( 5 );

dlaset.ndarray( 'all', 2, 2, 2.0, 1.0, A, 2, 1, 1 );
// A => <Float64Array>[ 0.0, 1.0, 2.0, 2.0, 1.0 ]

Notes

Examples

var ndarray2array = require( '@stdlib/ndarray/base/to-array' );
var uniform = require( '@stdlib/random/array/discrete-uniform' );
var numel = require( '@stdlib/ndarray/base/numel' );
var shape2strides = require( '@stdlib/ndarray/base/shape2strides' );
var dlaset = require( '@stdlib/lapack/base/dlaset' );

var shape = [ 5, 8 ];
var order = 'row-major';
var strides = shape2strides( shape, order );

var N = numel( shape );

var A = uniform( N, -10, 10, {
    'dtype': 'float64'
});
console.log( ndarray2array( A, shape, strides, 0, order ) );

dlaset( order, 'all', shape[ 0 ], shape[ 1 ], 2.0, 3.0, A, strides[ 0 ] );
console.log( ndarray2array( A, shape, strides, 0, order ) );

C APIs

Usage

#include "stdlib/lapack/base/dlaset.h"

c_dlaset( layout, uplo, M, N, alpha, beta, *A, LDA )

Sets the off-diagonal elements and the diagonal elements of a double-precision floating-point matrix to specified values.

#include "stdlib/lapack/base/dlaset.h"
#include "stdlib/lapack/base/shared.h"

double A[] = {
    1.0, 2.0,
    3.0, 4.0
};

c_dlaset( LAPACK_ROW_MAJOR, -1, 2, 2, 1.0, 2.0, A, 2 );

The function accepts the following arguments:

  • layout: [in] LAPACK_LAYOUT storage layout.
  • uplo: [in] int specifies whether to set the upper or lower triangular/trapezoidal part of a matrix A.
  • M: [in] LAPACK_INT number of rows in A.
  • N: [in] LAPACK_INT number of columns in A.
  • alpha: [in] double value assigned to off-diagonal elements.
  • beta: [in] double value assigned to diagonal elements.
  • A: [out] double* output matrix.
  • LDA: [in] LAPACK_INT stride of the first dimension of A (a.k.a., leading dimension of the matrix A).
LAPACK_INT c_dlaset( const LAPACK_LAYOUT layout, const int uplo, const LAPACK_INT M, const LAPACK_INT N, const double alpha, const double beta, double *A, const LAPACK_INT LDA );

c_dlaset_ndarray( uplo, M, N, alpha, beta, *A, sa1, sa2, oa )

Sets the off-diagonal elements and the diagonal elements of a double-precision floating-point matrix to specified values using alternative indexing semantics.

#include "stdlib/lapack/base/dlaset.h"
#include "stdlib/lapack/base/shared.h"

double A[] = {
    1.0, 2.0,
    3.0, 4.0
};

c_dlaset_ndarray( -1, 2, 2, 1.0, 2.0, A, 2, 1, 0 );

The function accepts the following arguments:

  • uplo: [in] int specifies whether to set the upper or lower triangular/trapezoidal part of a matrix A.
  • M: [in] LAPACK_INT number of rows in A.
  • N: [in] LAPACK_INT number of columns in A.
  • alpha: [in] double value assigned to off-diagonal elements.
  • beta: [in] double value assigned to diagonal elements.
  • A: [out] double* output matrix.
  • sa1: [in] LAPACK_INT stride of the first dimension of A.
  • sa2: [in] LAPACK_INT stride of the second dimension of A.
  • oa: [in] LAPACK_INT starting index for A.
LAPACK_INT c_dlaset_ndarray( const int uplo, const LAPACK_INT M, const LAPACK_INT N, const double alpha, const double beta, double *A, const LAPACK_INT strideA1, const LAPACK_INT strideA2, const LAPACK_INT offsetA );

Examples

#include "stdlib/lapack/base/dlaset.h"
#include "stdlib/lapack/base/shared.h"
#include <stdio.h>

int main( void ) {
    // Define a 3x3 matrix:
    double A[ 3*3 ] = {
        1.0, 2.0, 3.0,
        4.0, 5.0, 6.0,
        7.0, 8.0, 9.0
    };

    // Specify the number of elements along each dimension of `A`:
    const int M = 3;
    const int N = 3;

    // Set elements of the upper triangle of `A` to 1.0 (off-diagonal) and 2.0 (diagonal):
    c_dlaset( LAPACK_ROW_MAJOR, LAPACK_UPPER_TRIANGLE, M, N, 1.0, 2.0, A, N );

    // Print the result:
    for ( int i = 0; i < M; i++ ) {
        for ( int j = 0; j < N; j++ ) {
            printf( "A[ %i, %i ] = %lf\n", i, j, A[ (i*N)+j ] );
        }
    }

    // Set elements of the lower triangle of `A` to 3.0 (off-diagonal) and 4.0 (diagonal) using alternative indexing semantics:
    c_dlaset_ndarray( LAPACK_LOWER_TRIANGLE, M, N, 3.0, 4.0, A, N, 1, 0 );

    // Print the result:
    for ( int i = 0; i < M; i++ ) {
        for ( int j = 0; j < N; j++ ) {
            printf( "A[ %i, %i ] = %lf\n", i, j, A[ (i*N)+j ] );
        }
    }
}