feat: add C ndarray implementation for blas/base/dscal

lib/node_modules/@stdlib/blas/base/dscal/README.md

@@ -77,7 +77,7 @@ dscal( 3, 5.0, x1, 2 );
 // x0 => <Float64Array>[ 1.0, -10.0, 3.0, -20.0, 5.0, -30.0 ]
 ```
 
-If either `N` or `stride` is less than or equal to `0`, the function returns `x` unchanged.
+If `N` is less than or equal to `0`, the function returns `x` unchanged.
 
 #### dscal.ndarray( N, alpha, x, stride, offset )
 
@@ -193,6 +193,28 @@ The function accepts the following arguments:
 void c_dscal( const CBLAS_INT N, const double alpha, double *X, const CBLAS_INT stride );
 ```
 
+#### c_dscal_ndarray( N, alpha, \*X, stride, offset )
+
+Multiplies each element of a double-precision floating-point vector by a constant using alternative indexing semantics.
+
+```c
+double x[] = { 1.0, 2.0, 3.0, 4.0 };
+
+c_dscal_ndarray( 4, 5.0, x, 1, 0 );
+```
+
+The function accepts the following arguments:
+
+-   **N**: `[in] CBLAS_INT` number of indexed elements.
+-   **alpha**: `[in] double` scalar constant.
+-   **X**: `[inout] double*` input array.
+-   **stride**: `[in] CBLAS_INT` index increment for `X`.
+-   **offset**: `[in] CBLAS_INT` starting index for `X`.
+
+```c
+void c_dscal_ndarray( const CBLAS_INT N, const double alpha, double *X, const CBLAS_INT stride, const CBLAS_INT offset );
+```
+
 </section>
 
 <!-- /.usage -->
@@ -223,10 +245,18 @@ int main( void ) {
     const int N = 8;
 
     // Specify a stride:
-    const int strideX = 1;
+    const int stride = 1;
+
+    // Scale the vector:
+    c_dscal( N, 5.0, x, stride );
+
+    // Print the result:
+    for ( int i = 0; i < 8; i++ ) {
+        printf( "x[ %i ] = %lf\n", i, x[ i ] );
+    }
 
     // Scale the vector:
-    c_dscal( N, 5.0, x, strideX );
+    c_dscal_ndarray( N, 5.0, x, -stride, N-1 );
 
     // Print the result:
     for ( int i = 0; i < 8; i++ ) {

lib/node_modules/@stdlib/blas/base/dscal/benchmark/c/benchmark.length.c

@@ -94,7 +94,7 @@ static double rand_double( void ) {
 * @param len          array length
 * @return elapsed time in seconds
 */
-static double benchmark( int iterations, int len ) {
+static double benchmark1( int iterations, int len ) {
 	double elapsed;
 	double x[ len ];
 	double t;
@@ -118,6 +118,37 @@ static double benchmark( int iterations, int len ) {
 	return elapsed;
 }
 
+/**
+* Runs a benchmark.
+*
+* @param iterations   number of iterations
+* @param len          array length
+* @return elapsed time in seconds
+*/
+static double benchmark2( int iterations, int len ) {
+	double elapsed;
+	double x[ len ];
+	double t;
+	int i;
+
+	for ( i = 0; i < len; i++ ) {
+		x[ i ] = ( rand_double()*200.0 ) - 100.0;
+	}
+	t = tic();
+	for ( i = 0; i < iterations; i++ ) {
+		c_dscal_ndarray( len, 5.0, x, 1, 0 );
+		if ( x[ 0 ] != x[ 0 ] ) {
+			printf( "should not return NaN\n" );
+			break;
+		}
+	}
+	elapsed = tic() - t;
+	if ( x[ 0 ] != x[ 0 ] ) {
+		printf( "should not return NaN\n" );
+	}
+	return elapsed;
+}
+
 /**
 * Main execution sequence.
 */
@@ -140,7 +171,14 @@ int main( void ) {
 		for ( j = 0; j < REPEATS; j++ ) {
 			count += 1;
 			printf( "# c::%s:len=%d\n", NAME, len );
-			elapsed = benchmark( iter, len );
+			elapsed = benchmark1( iter, len );
+			print_results( iter, elapsed );
+			printf( "ok %d benchmark finished\n", count );
+		}
+		for ( j = 0; j < REPEATS; j++ ) {
+			count += 1;
+			printf( "# c::%s:ndarray:len=%d\n", NAME, len );
+			elapsed = benchmark2( iter, len );
 			print_results( iter, elapsed );
 			printf( "ok %d benchmark finished\n", count );
 		}

lib/node_modules/@stdlib/blas/base/dscal/docs/repl.txt

@@ -9,7 +9,7 @@
     Indexing is relative to the first index. To introduce an offset, use typed
     array views.
 
-    If `N <= 0` or `stride <= 0`, the function returns `x` unchanged.
+    If `N <= 0` the function returns `x` unchanged.
 
     Parameters
     ----------

lib/node_modules/@stdlib/blas/base/dscal/docs/types/index.d.ts

@@ -28,7 +28,7 @@ interface Routine {
 	* @param N - number of indexed elements
 	* @param alpha - constant
 	* @param x - input array
-	* @param stride - stride length
+	* @param stride - index increment
 	* @returns input array
 	*
 	* @example
@@ -47,7 +47,7 @@ interface Routine {
 	* @param N - number of indexed elements
 	* @param alpha - constant
 	* @param x - input array
-	* @param stride - stride length
+	* @param stride - index increment
 	* @param offset - starting index
 	* @returns input array
 	*
@@ -68,7 +68,7 @@ interface Routine {
 * @param N - number of indexed elements
 * @param alpha - constant
 * @param x - input array
-* @param stride - stride length
+* @param stride - index increment
 * @returns input array
 *
 * @example

lib/node_modules/@stdlib/blas/base/dscal/examples/c/example.c

@@ -36,4 +36,12 @@ int main( void ) {
 	for ( int i = 0; i < 8; i++ ) {
 		printf( "x[ %i ] = %lf\n", i, x[ i ] );
 	}
+
+	// Scale the vector:
+	c_dscal_ndarray( N, 5.0, x, -strideX, N-1 );
+
+	// Print the result:
+	for ( int i = 0; i < 8; i++ ) {
+		printf( "x[ %i ] = %lf\n", i, x[ i ] );
+	}
 }

lib/node_modules/@stdlib/blas/base/dscal/include/stdlib/blas/base/dscal.h

@@ -36,6 +36,11 @@ extern "C" {
 */
 void API_SUFFIX(c_dscal)( const CBLAS_INT N, const double alpha, double *X, const CBLAS_INT stride );
 
+/**
+* Multiplies each element of a double-precision floating-point vector by a constant using alternative indexing semantics.
+*/
+void API_SUFFIX(c_dscal_ndarray)( const CBLAS_INT N, const double alpha, double *X, const CBLAS_INT stride, const CBLAS_INT offset );
+
 #ifdef __cplusplus
 }
 #endif

lib/node_modules/@stdlib/blas/base/dscal/lib/dscal.js

@@ -18,9 +18,10 @@
 
 'use strict';
 
-// VARIABLES //
+// MODULES //
 
-var M = 5;
+var stride2offset = require( '@stdlib/strided/base/stride2offset' );
+var ndarray = require( './ndarray.js' );
 
 
 // MAIN //
@@ -31,7 +32,7 @@ var M = 5;
 * @param {PositiveInteger} N - number of indexed elements
 * @param {number} alpha - scalar
 * @param {Float64Array} x - input array
-* @param {PositiveInteger} stride - index increment
+* @param {integer} stride - index increment
 * @returns {Float64Array} input array
 *
 * @example
@@ -43,39 +44,8 @@ var M = 5;
 * // x => <Float64Array>[ -10.0, 5.0, 15.0, -25.0, 20.0, 0.0, -5.0, -15.0 ]
 */
 function dscal( N, alpha, x, stride ) {
-	var i;
-	var m;
-
-	if ( N <= 0 || stride <= 0 || alpha === 1.0 ) {
-		return x;
-	}
-	// Use loop unrolling if the stride is equal to `1`...
-	if ( stride === 1 ) {
-		m = N % M;
-
-		// If we have a remainder, run a clean-up loop...
-		if ( m > 0 ) {
-			for ( i = 0; i < m; i++ ) {
-				x[ i ] *= alpha;
-			}
-		}
-		if ( N < M ) {
-			return x;
-		}
-		for ( i = m; i < N; i += M ) {
-			x[ i ] *= alpha;
-			x[ i+1 ] *= alpha;
-			x[ i+2 ] *= alpha;
-			x[ i+3 ] *= alpha;
-			x[ i+4 ] *= alpha;
-		}
-		return x;
-	}
-	N *= stride;
-	for ( i = 0; i < N; i += stride ) {
-		x[ i ] *= alpha;
-	}
-	return x;
+	var ox = stride2offset( N, stride );
+	return ndarray( N, alpha, x, stride, ox );
 }
 
 

lib/node_modules/@stdlib/blas/base/dscal/lib/dscal.native.js

@@ -31,7 +31,7 @@ var addon = require( './../src/addon.node' );
 * @param {PositiveInteger} N - number of indexed elements
 * @param {number} alpha - scalar
 * @param {Float64Array} x - input array
-* @param {PositiveInteger} stride - index increment
+* @param {integer} stride - index increment
 * @returns {Float64Array} input array
 *
 * @example

lib/node_modules/@stdlib/blas/base/dscal/lib/ndarray.native.js

@@ -20,9 +20,7 @@
 
 // MODULES //
 
-var minViewBufferIndex = require( '@stdlib/strided/base/min-view-buffer-index' );
-var offsetView = require( '@stdlib/strided/base/offset-view' );
-var addon = require( './dscal.native.js' );
+var addon = require( './../src/addon.node' );
 
 
 // MAIN //
@@ -46,13 +44,7 @@ var addon = require( './dscal.native.js' );
 * // x => <Float64Array>[ 1.0, -2.0, 3.0, -20.0, 25.0, -30.0 ]
 */
 function dscal( N, alpha, x, stride, offset ) {
-	var view;
-	offset = minViewBufferIndex( N, stride, offset );
-	if ( stride < 0 ) {
-		stride *= -1;
-	}
-	view = offsetView( x, offset );
-	addon( N, alpha, view, stride );
+	addon.ndarray( N, alpha, x, stride, offset );
 	return x;
 }