feat: add support for negative strides in idamax and isamax

PR-URL: stdlib-js#2793 Closes: stdlib-js#2792 Ref: stdlib-js#2464 Reviewed-by: Athan Reines <[email protected]>
gunjjoshi · Aug 21, 2024 · 99609cc · 99609cc
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Showing 12 changed files with 49 additions and 35 deletions.
diff --git a/lib/node_modules/@stdlib/blas/base/idamax/README.md b/lib/node_modules/@stdlib/blas/base/idamax/README.md
@@ -112,7 +112,7 @@ var idx = idamax.ndarray( 5, x, 1, 1 );
 
 ## Notes
 
-- If `N < 1` or `strideX <= 0`, both functions return `-1`.
+- If `N < 1`, both functions return `-1`.
 - `idamax()` corresponds to the [BLAS][blas] level 1 function [`idamax`][idamax].
 
 </section>
@@ -157,7 +157,7 @@ console.log( idx );
 
 [blas]: http://www.netlib.org/blas
 
-[idamax]: http://www.netlib.org/lapack/explore-html/de/da4/group__double__blas__level1.html
+[idamax]: https://netlib.org/lapack/explore-html/dd/de0/idamax_8f_source.html
 
 [@stdlib/array/float64]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/float64
 

diff --git a/lib/node_modules/@stdlib/blas/base/idamax/docs/repl.txt b/lib/node_modules/@stdlib/blas/base/idamax/docs/repl.txt
@@ -8,7 +8,7 @@
  Indexing is relative to the first index. To introduce an offset, use typed
  array views.
 
- If `N < 1` or `strideX <= 0`, the function returns `-1`.
+ If `N < 1`, both functions return `-1`.
 
  Parameters
  ----------

diff --git a/lib/node_modules/@stdlib/blas/base/idamax/lib/ndarray.js b/lib/node_modules/@stdlib/blas/base/idamax/lib/ndarray.js
@@ -49,7 +49,7 @@ function idamax( N, x, strideX, offsetX ) {
  var v;
  var i;
 
- if ( N < 1 || strideX <= 0 ) {
+ if ( N < 1 ) {
  return -1;
  }
  idx = 0;

diff --git a/lib/node_modules/@stdlib/blas/base/idamax/lib/ndarray.native.js b/lib/node_modules/@stdlib/blas/base/idamax/lib/ndarray.native.js
@@ -48,6 +48,9 @@ function idamax( N, x, strideX, offsetX ) {
  var viewX;
  offsetX = minViewBufferIndex( N, strideX, offsetX );
  viewX = offsetView( x, offsetX );
+ if ( strideX < 0 ) {
+ return N - 1 - addon( N, viewX, -strideX );
+ }
  return addon( N, viewX, strideX );
 }
 

diff --git a/lib/node_modules/@stdlib/blas/base/idamax/test/test.ndarray.js b/lib/node_modules/@stdlib/blas/base/idamax/test/test.ndarray.js
@@ -108,19 +108,21 @@ tape( 'if provided an `N` parameter equal to `1`, the function returns `0`', fun
  t.end();
 });
 
-tape( 'if provided a `strideX` parameter less than or equal to `0`, the function returns `-1`', function test( t ) {
- var expected;
+tape( 'the function supports accessing elements in reverse order', function test( t ) {
  var idx;
  var x;
 
  x = new Float64Array( [ 3.0, -4.0, 1.0, 15.0, 4.0, 3.0 ] );
- expected = -1;
 
- idx = idamax( x.length, x, 0, 0 );
- t.strictEqual( idx, expected, 'returns expected value' );
+ idx = idamax( x.length, x, -1, x.length-1 );
+ t.strictEqual( idx, 2, 'returns expected value' );
 
- idx = idamax( x.length, x, -1, 0 );
- t.strictEqual( idx, expected, 'returns expected value' );
+ idx = idamax( 3, x, -1, x.length-4 );
+ t.strictEqual( idx, 1, 'returns expected value' );
+
+ x = new Float64Array( [ 3.0, 999.9, 999.9, -4.0, 999.9, 999.9, 1.0, 999.9, 999.9, 15.0, 999.9, 999.9, 4.0, 999.9, 999.9, 3.0 ] );
+ idx = idamax( 6, x, -3, x.length-1 );
+ t.strictEqual( idx, 2, 'returns expected value' );
 
  t.end();
 });

diff --git a/lib/node_modules/@stdlib/blas/base/idamax/test/test.ndarray.native.js b/lib/node_modules/@stdlib/blas/base/idamax/test/test.ndarray.native.js
@@ -117,19 +117,21 @@ tape( 'if provided an `N` parameter equal to `1`, the function returns `0`', opt
  t.end();
 });
 
-tape( 'if provided a `strideX` parameter less than or equal to `0`, the function returns `-1`', opts, function test( t ) {
- var expected;
+tape( 'the function supports accessing elements in reverse order', function test( t ) {
  var idx;
  var x;
 
  x = new Float64Array( [ 3.0, -4.0, 1.0, 15.0, 4.0, 3.0 ] );
- expected = -1;
 
- idx = idamax( x.length, x, 0, 0 );
- t.strictEqual( idx, expected, 'returns expected value' );
+ idx = idamax( x.length, x, -1, x.length-1 );
+ t.strictEqual( idx, 2, 'returns expected value' );
 
- idx = idamax( x.length, x, -1, 5 );
- t.strictEqual( idx, expected, 'returns expected value' );
+ idx = idamax( 3, x, -1, x.length-4 );
+ t.strictEqual( idx, 1, 'returns expected value' );
+
+ x = new Float64Array( [ 3.0, 999.9, 999.9, -4.0, 999.9, 999.9, 1.0, 999.9, 999.9, 15.0, 999.9, 999.9, 4.0, 999.9, 999.9, 3.0 ] );
+ idx = idamax( 6, x, -3, x.length-1 );
+ t.strictEqual( idx, 2, 'returns expected value' );
 
  t.end();
 });

diff --git a/lib/node_modules/@stdlib/blas/base/isamax/README.md b/lib/node_modules/@stdlib/blas/base/isamax/README.md
@@ -112,7 +112,7 @@ var idx = isamax.ndarray( 5, x, 1, 1 );
 
 ## Notes
 
-- If `N < 1` or `strideX <= 0`, both functions return `-1`.
+- If `N < 1`, both functions return `-1`.
 - `isamax()` corresponds to the [BLAS][blas] level 1 function [`isamax`][isamax].
 
 </section>

diff --git a/lib/node_modules/@stdlib/blas/base/isamax/docs/repl.txt b/lib/node_modules/@stdlib/blas/base/isamax/docs/repl.txt
@@ -8,7 +8,7 @@
  Indexing is relative to the first index. To introduce an offset, use typed
  array views.
 
- If `N < 1` or `strideX <= 0`, the function returns `-1`.
+ If `N < 1`, both functions return `-1`.
 
  Parameters
  ----------

diff --git a/lib/node_modules/@stdlib/blas/base/isamax/lib/ndarray.js b/lib/node_modules/@stdlib/blas/base/isamax/lib/ndarray.js
@@ -49,7 +49,7 @@ function isamax( N, x, strideX, offsetX ) {
  var v;
  var i;
 
- if ( N < 1 || strideX <= 0 ) {
+ if ( N < 1 ) {
  return -1;
  }
  idx = 0;

diff --git a/lib/node_modules/@stdlib/blas/base/isamax/lib/ndarray.native.js b/lib/node_modules/@stdlib/blas/base/isamax/lib/ndarray.native.js
@@ -48,6 +48,9 @@ function isamax( N, x, strideX, offsetX ) {
  var viewX;
  offsetX = minViewBufferIndex( N, strideX, offsetX );
  viewX = offsetView( x, offsetX );
+ if ( strideX < 0 ) {
+ return N - 1 - addon( N, viewX, -strideX );
+ }
  return addon( N, viewX, strideX );
 }
 

diff --git a/lib/node_modules/@stdlib/blas/base/isamax/test/test.ndarray.js b/lib/node_modules/@stdlib/blas/base/isamax/test/test.ndarray.js
@@ -108,19 +108,21 @@ tape( 'if provided an `N` parameter equal to `1`, the function returns `0`', fun
  t.end();
 });
 
-tape( 'if provided a `strideX` parameter less than or equal to `0`, the function returns `-1`', function test( t ) {
- var expected;
+tape( 'the function supports accessing elements in reverse order', function test( t ) {
  var idx;
  var x;
 
  x = new Float32Array( [ 3.0, -4.0, 1.0, 15.0, 4.0, 3.0 ] );
- expected = -1;
 
- idx = isamax( x.length, x, 0, 0 );
- t.strictEqual( idx, expected, 'returns expected value' );
+ idx = isamax( x.length, x, -1, x.length-1 );
+ t.strictEqual( idx, 2, 'returns expected value' );
 
- idx = isamax( x.length, x, -1, 0 );
- t.strictEqual( idx, expected, 'returns expected value' );
+ idx = isamax( 3, x, -1, x.length-4 );
+ t.strictEqual( idx, 1, 'returns expected value' );
+
+ x = new Float32Array( [ 3.0, 999.9, 999.9, -4.0, 999.9, 999.9, 1.0, 999.9, 999.9, 15.0, 999.9, 999.9, 4.0, 999.9, 999.9, 3.0 ] );
+ idx = isamax( 6, x, -3, x.length-1 );
+ t.strictEqual( idx, 2, 'returns expected value' );
 
  t.end();
 });

diff --git a/lib/node_modules/@stdlib/blas/base/isamax/test/test.ndarray.native.js b/lib/node_modules/@stdlib/blas/base/isamax/test/test.ndarray.native.js
@@ -117,19 +117,21 @@ tape( 'if provided an `N` parameter equal to `1`, the function returns `0`', opt
  t.end();
 });
 
-tape( 'if provided a `strideX` parameter less than or equal to `0`, the function returns `-1`', opts, function test( t ) {
- var expected;
+tape( 'the function supports accessing elements in reverse order', function test( t ) {
  var idx;
  var x;
 
  x = new Float32Array( [ 3.0, -4.0, 1.0, 15.0, 4.0, 3.0 ] );
- expected = -1;
 
- idx = isamax( x.length, x, 0, 0 );
- t.strictEqual( idx, expected, 'returns expected value' );
+ idx = isamax( x.length, x, -1, x.length-1 );
+ t.strictEqual( idx, 2, 'returns expected value' );
 
- idx = isamax( x.length, x, -1, 5 );
- t.strictEqual( idx, expected, 'returns expected value' );
+ idx = isamax( 3, x, -1, x.length-4 );
+ t.strictEqual( idx, 1, 'returns expected value' );
+
+ x = new Float32Array( [ 3.0, 999.9, 999.9, -4.0, 999.9, 999.9, 1.0, 999.9, 999.9, 15.0, 999.9, 999.9, 4.0, 999.9, 999.9, 3.0 ] );
+ idx = isamax( 6, x, -3, x.length-1 );
+ t.strictEqual( idx, 2, 'returns expected value' );
 
  t.end();
 });