Skip to content

feat: add blas/ext/base/dfirst-index-less-than #13361

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
headlessNode wants to merge 3 commits into
base: develop
Choose a base branch
from
+3,972 −0
Open

feat: add blas/ext/base/dfirst-index-less-than #13361

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
28c49d5
feat: add blas/ext/base/dfirst-index-less-than
headlessNode Jul 7, 2026
40cf627
fix: cleanup
headlessNode Jul 7, 2026
47ae89d
fix: cleanup
headlessNode Jul 7, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
346 changes: 346 additions & 0 deletions lib/node_modules/@stdlib/blas/ext/base/dfirst-index-less-than/README.md
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,346 @@
<!--

@license Apache-2.0

Copyright (c) 2026 The Stdlib Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

-->

# dfirstIndexLessThan

> Return the index of the first element in a double-precision floating-point strided array which is less than a corresponding element in another double-precision floating-point strided array.

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- Package usage documentation. -->

<section class="usage">

## Usage

```javascript
var dfirstIndexLessThan = require( '@stdlib/blas/ext/base/dfirst-index-less-than' );
```

#### dfirstIndexLessThan( N, x, strideX, y, strideY )

Returns the index of the first element in a double-precision floating-point strided array which is less than a corresponding element in another double-precision floating-point strided array.

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

var x = new Float64Array( [ 0.0, 0.0, 0.0, 0.0 ] );
var y = new Float64Array( [ 0.0, 0.0, 1.0, 0.0 ] );

var idx = dfirstIndexLessThan( x.length, x, 1, y, 1 );
// returns 2
```

The function has the following parameters:

- **N**: number of indexed elements.
- **x**: first input [`Float64Array`][@stdlib/array/float64].
- **strideX**: stride length for `x`.
- **y**: second input [`Float64Array`][@stdlib/array/float64].
- **strideY**: stride length for `y`.

If the function is unable to find an element in `x` which is less than a corresponding element in `y`, the function returns `-1`.

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

var x = new Float64Array( [ 5.0, 6.0, 7.0, 8.0 ] );
var y = new Float64Array( [ 1.0, 2.0, 3.0, 4.0 ] );

var idx = dfirstIndexLessThan( x.length, x, 1, y, 1 );
// returns -1
```

The `N` and stride parameters determine which elements in the strided arrays are accessed at runtime. For example, to compare every other element:

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

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float64Array( [ 0.0, 9.0, 0.0, 9.0, 9.0, 9.0 ] );

var idx = dfirstIndexLessThan( 3, x, 2, y, 2 );
// returns 2
```

Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.

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

// Initial arrays...
var x0 = new Float64Array( [ 1.0, 2.0, 3.0, 4.0 ] );
var y0 = new Float64Array( [ 9.0, 0.0, 9.0, 9.0 ] );

// Create offset views...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Find index...
var idx = dfirstIndexLessThan( 2, x1, 1, y1, 1 );
// returns 1
```

<!-- lint disable maximum-heading-length -->

#### dfirstIndexLessThan.ndarray( N, x, strideX, offsetX, y, strideY, offsetY )

<!-- lint enable maximum-heading-length -->

Returns the index of the first element in a double-precision floating-point strided array which is less than a corresponding element in another double-precision floating-point strided array using alternative indexing semantics.

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

var x = new Float64Array( [ 0.0, 0.0, 0.0, 0.0 ] );
var y = new Float64Array( [ 0.0, 0.0, 1.0, 0.0 ] );

var idx = dfirstIndexLessThan.ndarray( x.length, x, 1, 0, y, 1, 0 );
// returns 2
```

The function has the following additional parameters:

- **offsetX**: starting index for `x`.
- **offsetY**: starting index for `y`.

While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to access only the last three elements of each strided array:

<!-- eslint-disable max-len -->

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

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float64Array( [ 9.0, 9.0, 9.0, 0.0, 9.0, 9.0 ] );

var idx = dfirstIndexLessThan.ndarray( 3, x, 1, x.length-3, y, 1, y.length-3 );
// returns 1
```

</section>

<!-- /.usage -->

<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

## Notes

- When comparing elements, the function checks whether an element in `x` is less than a corresponding element in `y` using the less-than operator `<`. As a consequence, comparisons involving `NaN` always evaluate to `false`.

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var dfirstIndexLessThan = require( '@stdlib/blas/ext/base/dfirst-index-less-than' );

var x = discreteUniform( 10, 0, 10, {
'dtype': 'float64'
});
console.log( x );

var y = discreteUniform( 10, 0, 10, {
'dtype': 'float64'
});
console.log( y );

var idx = dfirstIndexLessThan( x.length, x, 1, y, 1 );
console.log( idx );
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/blas/ext/base/dfirst_index_less_than.h"
```

#### stdlib_strided_dfirst_index_less_than( N, \*X, strideX, \*Y, strideY )

Returns the index of the first element in a double-precision floating-point strided array which is less than a corresponding element in another double-precision floating-point strided array.

```c
double x[] = { 0.0, 0.0, 0.0, 0.0 };
double y[] = { 0.0, 0.0, 1.0, 0.0 };

int idx = stdlib_strided_dfirst_index_less_than( 4, x, 1, y, 1 );
// returns 2
```

The function accepts the following arguments:

- **N**: `[in] CBLAS_INT` number of indexed elements.
- **X**: `[in] double*` first input array.
- **strideX**: `[in] CBLAS_INT` stride length.
- **Y**: `[in] double*` second input array.
- **strideY**: `[in] CBLAS_INT` stride length.

```c
CBLAS_INT stdlib_strided_dfirst_index_less_than( const CBLAS_INT N, const double *X, const CBLAS_INT strideX, const double *Y, const CBLAS_INT strideY );
```

<!-- lint disable maximum-heading-length -->

#### stdlib_strided_dfirst_index_less_than_ndarray( N, \*X, strideX, offsetX, \*Y, strideY, offsetY )

<!-- lint enable maximum-heading-length -->

Returns the index of the first element in a double-precision floating-point strided array which is less than a corresponding element in another double-precision floating-point strided array using alternative indexing semantics.

```c
double x[] = { 0.0, 0.0, 0.0, 0.0 };
double y[] = { 0.0, 0.0, 1.0, 0.0 };

int idx = stdlib_strided_dfirst_index_less_than_ndarray( 4, x, 1, 0, y, 1, 0 );
// returns 2
```

The function accepts the following arguments:

- **N**: `[in] CBLAS_INT` number of indexed elements.
- **X**: `[in] double*` first input array.
- **strideX**: `[in] CBLAS_INT` stride length.
- **offsetX**: `[in] CBLAS_INT` starting index.
- **Y**: `[in] double*` second input array.
- **strideY**: `[in] CBLAS_INT` stride length.
- **offsetY**: `[in] CBLAS_INT` starting index.

```c
CBLAS_INT stdlib_strided_dfirst_index_less_than_ndarray( const CBLAS_INT N, const double *X, const CBLAS_INT strideX, const CBLAS_INT offsetX, const double *Y, const CBLAS_INT strideY, const CBLAS_INT offsetY );
```

</section>

<!-- /.usage -->

<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- C API usage examples. -->

<section class="examples">

### Examples

```c
#include "stdlib/blas/ext/base/dfirst_index_less_than.h"
#include <stdio.h>

int main( void ) {
// Create strided arrays:
const double x[] = { 1.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0, 0.0 };
const double y[] = { 1.0, 0.0, 1.0, 0.0, 1.0, 0.0, 1.0, 0.0 };

// Specify the number of indexed elements:
const int N = 8;

// Specify stride lengths:
const int strideX = 1;
const int strideY = 1;

// Perform a search:
int idx = stdlib_strided_dfirst_index_less_than( N, x, strideX, y, strideY );

// Print the result:
printf( "index value: %d\n", idx );
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="references">

</section>

<!-- /.references -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="links">

[@stdlib/array/float64]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/float64

[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray

</section>

<!-- /.links -->
Loading