feat: add `lapack/base/dlacn2` #7438

aayush0325 · 2025-06-21T13:11:30Z

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This pull request:

adds lapack/base/dlacn2

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Read, understood, and followed the contributing guidelines.

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stdlib-bot · 2025-06-22T17:13:50Z

Coverage Report

Package	Statements	Branches	Functions	Lines
lapack/base/dlacn2	$\color{red}796/823$ $\color{green}+96.72\%$	$\color{red}45/50$ $\color{green}+90.00\%$	$\color{green}10/10$ $\color{green}+100.00\%$	$\color{red}796/823$ $\color{green}+96.72\%$

The above coverage report was generated for the changes in this PR.

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kgryte · 2025-06-25T17:18:17Z

lib/node_modules/@stdlib/lapack/base/dlacn2/README.md

+
+#### dlacn2( N, V, X, ISGN, EST, KASE, ISAVE )
+
+Estimates the one-norm of a square matrix `A`, using alternative indexing semantics and reverse communication for evaluating matrix-vector products.


Suggested change

Estimates the one-norm of a square matrix `A`, using alternative indexing semantics and reverse communication for evaluating matrix-vector products.

Estimates the one-norm of a square matrix `A`, using reverse communication for evaluating matrix-vector products.

kgryte · 2025-06-25T17:19:29Z

lib/node_modules/@stdlib/lapack/base/dlacn2/README.md

+-   **V**: workspace [`Float64Array`][mdn-float64array] having `N` indexed elements, used internally to store intermediate vectors.
+-   **X**: input/output [`Float64Array`][mdn-float64array] having `N` indexed elements, contains the current or next matrix-vector product.
+-   **ISGN**: [`Int32Array`][mdn-int32array] having `N` indexed elements, stores the sign of each element in `X` during iterations.
+-   **EST**: single-element [`Float64Array`][mdn-float64array], on output, contains the estimated one-norm of the matrix `A`.
+-   **KASE**: single-element [`Int32Array`][mdn-int32array] that controls the reverse communication.
+-   **ISAVE**: [`Int32Array`][mdn-int32array] having 3 indexed elements, used internally to maintain state across multiple calls.


Suggested change

- **V**: workspace [`Float64Array`][mdn-float64array] having `N` indexed elements, used internally to store intermediate vectors.

- **X**: input/output [`Float64Array`][mdn-float64array] having `N` indexed elements, contains the current or next matrix-vector product.

- **ISGN**: [`Int32Array`][mdn-int32array] having `N` indexed elements, stores the sign of each element in `X` during iterations.

- **EST**: single-element [`Float64Array`][mdn-float64array], on output, contains the estimated one-norm of the matrix `A`.

- **KASE**: single-element [`Int32Array`][mdn-int32array] that controls the reverse communication.

- **ISAVE**: [`Int32Array`][mdn-int32array] having 3 indexed elements, used internally to maintain state across multiple calls.

- **V**: workspace [`Float64Array`][mdn-float64array] having `N` indexed elements. This workspace is used internally to store intermediate vectors.

- **X**: input/output [`Float64Array`][mdn-float64array] having `N` indexed elements. This array contains the current or next matrix-vector product.

- **ISGN**: [`Int32Array`][mdn-int32array] having `N` indexed elements. This array stores the sign of each element in `X` during iterations.

- **EST**: single-element [`Float64Array`][mdn-float64array], on output. This array contains the estimated one-norm of the matrix `A`.

- **KASE**: single-element [`Int32Array`][mdn-int32array] that controls the reverse communication.

- **ISAVE**: [`Int32Array`][mdn-int32array] having 3 indexed elements. This array is used internally to maintain state across multiple calls.

Here and below.

kgryte · 2025-06-25T17:20:43Z

lib/node_modules/@stdlib/lapack/base/dlacn2/README.md

+-   **KASE**: single-element [`Int32Array`][mdn-int32array] that controls the reverse communication.
+-   **ISAVE**: [`Int32Array`][mdn-int32array] having 3 indexed elements, used internally to maintain state across multiple calls.
+
+The reverse communication takes place using `KASE`, it may have any of these values:


Suggested change

The reverse communication takes place using `KASE`, it may have any of these values:

The reverse communication takes place using `KASE`. The single-element in `KASE` may have the following values:

kgryte · 2025-06-25T17:21:42Z

lib/node_modules/@stdlib/lapack/base/dlacn2/lib/dlacn2.js

+*
+* ## Notes
+*
+* the reverse communication takes place using `KASE`, it may have any of these values:


Suggested change

* the reverse communication takes place using `KASE`, it may have any of these values:

* The reverse communication takes place using `KASE`, it may have any of these values:

kgryte · 2025-06-25T17:22:26Z

lib/node_modules/@stdlib/lapack/base/dlacn2/lib/ndarray.js

+*
+* ## Notes
+*
+* the reverse communication takes place using `KASE`, it may have any of these values:


Suggested change

* the reverse communication takes place using `KASE`, it may have any of these values:

* The reverse communication takes place using `KASE`. The single-element in `KASE` may have the following values:

kgryte · 2025-06-25T17:23:10Z

lib/node_modules/@stdlib/lapack/base/dlacn2/lib/nint.js

+* var out = nint( 4.5 );
+* // returns 4.0
+*/
+function nint( X ) {


TODO: replace once Karan's PR for round-nearest-even gets merged.

kgryte · 2025-06-25T17:24:23Z

lib/node_modules/@stdlib/lapack/base/dlacn2/lib/base.js

+var nint = require( './nint.js' );
+
+
+// MAIN //


Suggested change

// MAIN //

// FUNCTIONS //

And then add // MAIN // below for the main export.

kgryte · 2025-06-25T17:27:40Z

lib/node_modules/@stdlib/lapack/base/dlacn2/lib/base.js

+
+	jlast = ISAVE[ offsetISAVE + strideISAVE ];
+	ISAVE[ offsetISAVE + strideISAVE ] = idamax( N, X, strideX, offsetX );
+


I suggest making your expressions a bit tighter using temporary variables here for indices.

var ii1 = offsetISAVE + strideISAVE; var ii2 = ii1 + strideISAVE; // ... ISAVE[ ii1 ] && ISAVE[ ii2 ] // ... vi = ISAVE[ ii1 ]; // ... X[ offsetX + ( vi * strideX ) ]

kgryte · 2025-06-25T17:30:48Z

lib/node_modules/@stdlib/lapack/base/dlacn2/lib/base.js

+	ISAVE[ offsetISAVE + ( 2 * strideISAVE ) ] = 2;
+
+	ix = offsetX;
+	for ( i = 0; i < N; i++ ) {


This could be replaced with blas/ext/base/dfill.

kgryte · 2025-06-25T17:32:34Z

lib/node_modules/@stdlib/lapack/base/dlacn2/test/test.dlacn2.js

+		}
+		else if ( KASE[ 0 ] === 1 ) {


Suggested change

}

else if ( KASE[ 0 ] === 1 ) {

} else if ( KASE[ 0 ] === 1 ) {

kgryte · 2025-06-25T17:33:24Z

lib/node_modules/@stdlib/lapack/base/dlacn2/test/test.dlacn2.js

+		}
+	}
+
+	expectedEST = new Float64Array( [ 25.0 ] );


Suggested change

expectedEST = new Float64Array( [ 25.0 ] );

// Expected values determined via the reference Fortran routines in LAPACK:

expectedEST = new Float64Array( [ 25.0 ] );

kgryte · 2025-06-25T17:34:35Z

lib/node_modules/@stdlib/lapack/base/dlacn2/test/test.dlacn2.js

+		}
+		else if ( KASE[ 0 ] === 1 ) {


Suggested change

}

else if ( KASE[ 0 ] === 1 ) {

} else if ( KASE[ 0 ] === 1 ) {

kgryte · 2025-06-25T17:35:00Z

lib/node_modules/@stdlib/lapack/base/dlacn2/test/test.dlacn2.js

+		}
+		else if ( KASE[ 0 ] === 1 ) {


Suggested change

}

else if ( KASE[ 0 ] === 1 ) {

} else if ( KASE[ 0 ] === 1 ) {

kgryte · 2025-06-25T17:37:43Z

lib/node_modules/@stdlib/lapack/base/dlacn2/test/test.ndarray.js

+			break;
+		}
+		else if ( KASE[ 1 ] === 1 ) {
+			dgemv( 'no-transpose', 4, 4, 1.0, A, 4, 1, 0, X, 1, 1, 0, work, 1, 1 );


Suggested change

dgemv( 'no-transpose', 4, 4, 1.0, A, 4, 1, 0, X, 1, 1, 0, work, 1, 1 );

// A*x:

dgemv( 'no-transpose', 4, 4, 1.0, A, 4, 1, 0, X, 1, 1, 0, work, 1, 1 );

Is work strictly necessary here? Can we write directly to X with dgemv?

After looking at dgemv, agree with the choice to use a work array. Adding a comment still stands.

kgryte · 2025-06-25T17:38:02Z

lib/node_modules/@stdlib/lapack/base/dlacn2/test/test.ndarray.js

+			dgemv( 'no-transpose', 4, 4, 1.0, A, 4, 1, 0, X, 1, 1, 0, work, 1, 1 );
+			dcopy( 4, work, 1, 1, X, 1, 1 );
+		} else if ( KASE[ 1 ] === 2 ) {
+			dgemv( 'transpose', 4, 4, 1.0, A, 4, 1, 0, X, 1, 1, 0, work, 1, 1 );


Suggested change

dgemv( 'transpose', 4, 4, 1.0, A, 4, 1, 0, X, 1, 1, 0, work, 1, 1 );

// A^T * x:

dgemv( 'transpose', 4, 4, 1.0, A, 4, 1, 0, X, 1, 1, 0, work, 1, 1 );

kgryte · 2025-06-25T17:45:04Z

lib/node_modules/@stdlib/lapack/base/dlacn2/test/test.dlacn2.js

+
+	work = new Float64Array( 1 );
+
+	while ( true ) {


May be good to add a comment before the while loop explaining, conceptually, what you are doing here.

stdlib-bot added LAPACK Issue or pull request related to the Linear Algebra Package (LAPACK). Needs Review A pull request which needs code review. labels Jun 21, 2025

aayush0325 marked this pull request as draft June 22, 2025 04:59

stdlib-bot removed the Needs Review A pull request which needs code review. label Jun 22, 2025

aayush0325 added 2 commits June 22, 2025 14:05

aayush0325 added 7 commits June 22, 2025 17:53

aayush0325 mentioned this pull request Jun 23, 2025

Weekly Standup (2025-06-23) stdlib-js/google-summer-of-code#159

Open

aayush0325 added 3 commits June 23, 2025 16:02

aayush0325 added GSoC Google Summer of Code. gsoc: 2025 Google Summer of Code (2025). labels Jun 23, 2025

aayush0325 marked this pull request as ready for review June 23, 2025 18:02

stdlib-bot added the Needs Review A pull request which needs code review. label Jun 23, 2025

kgryte reviewed Jun 25, 2025

View reviewed changes


		#### dlacn2( N, V, X, ISGN, EST, KASE, ISAVE )

		Estimates the one-norm of a square matrix `A`, using alternative indexing semantics and reverse communication for evaluating matrix-vector products.

	The reverse communication takes place using `KASE`, it may have any of these values:
	The reverse communication takes place using `KASE`. The single-element in `KASE` may have the following values:

	* the reverse communication takes place using `KASE`, it may have any of these values:
	* The reverse communication takes place using `KASE`, it may have any of these values:


		jlast = ISAVE[ offsetISAVE + strideISAVE ];
		ISAVE[ offsetISAVE + strideISAVE ] = idamax( N, X, strideX, offsetX );

	}
	else if ( KASE[ 0 ] === 1 ) {
	} else if ( KASE[ 0 ] === 1 ) {

	expectedEST = new Float64Array( [ 25.0 ] );
	// Expected values determined via the reference Fortran routines in LAPACK:
	expectedEST = new Float64Array( [ 25.0 ] );

	dgemv( 'no-transpose', 4, 4, 1.0, A, 4, 1, 0, X, 1, 1, 0, work, 1, 1 );
	// A*x:
	dgemv( 'no-transpose', 4, 4, 1.0, A, 4, 1, 0, X, 1, 1, 0, work, 1, 1 );

	dgemv( 'transpose', 4, 4, 1.0, A, 4, 1, 0, X, 1, 1, 0, work, 1, 1 );
	// A^T * x:
	dgemv( 'transpose', 4, 4, 1.0, A, 4, 1, 0, X, 1, 1, 0, work, 1, 1 );

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feat: add lapack/base/dlacn2 #7438

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feat: add lapack/base/dlacn2 #7438

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aayush0325 commented Jun 21, 2025

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feat: add `lapack/base/dlacn2` #7438

feat: add `lapack/base/dlacn2` #7438

stdlib-bot commented Jun 22, 2025 •

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kgryte Jun 25, 2025 •

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