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feat: add blas/ext/base/sindex-of-greater-than-equal-sorted #15960

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356 changes: 356 additions & 0 deletions ...ode_modules/@stdlib/blas/ext/base/sindex-of-greater-than-equal-sorted/README.md
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<!--

@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.

-->

# sindexOfGreaterThanEqualSorted

> Return the index of the first element in a sorted single-precision floating-point strided array which is greater than or equal to a specified search element.

<!-- 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

<!-- eslint-disable id-length -->

```javascript
var sindexOfGreaterThanEqualSorted = require( '@stdlib/blas/ext/base/sindex-of-greater-than-equal-sorted' );
```

#### sindexOfGreaterThanEqualSorted( N, searchElement, x, strideX )

Returns the index of the first element in a sorted single-precision floating-point strided array which is greater than or equal to a specified search element.

<!-- eslint-disable id-length -->

```javascript
var Float32Array = require( '@stdlib/array/float32' );

var x = new Float32Array( [ 1.0, 2.0, 2.0, 3.0 ] );

var idx = sindexOfGreaterThanEqualSorted( x.length, 2.0, x, 1 );
// returns 1

x = new Float32Array( [ 3.0, 2.0, 2.0, 1.0 ] );

idx = sindexOfGreaterThanEqualSorted( x.length, 2.0, x, 1 );
// returns 0
```

The function has the following parameters:

- **N**: number of indexed elements.
- **searchElement**: search element.
- **x**: sorted input [`Float32Array`][@stdlib/array/float32].
- **strideX**: stride length.

If the function is unable to find an element which is greater than or equal to a specified search element, the function returns `-1`.

<!-- eslint-disable id-length -->

```javascript
var Float32Array = require( '@stdlib/array/float32' );

var x = new Float32Array( [ 1.0, 2.0, 2.0, 3.0 ] );

var idx = sindexOfGreaterThanEqualSorted( x.length, 4.0, x, 1 );
// returns -1
```

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

<!-- eslint-disable id-length -->

```javascript
var Float32Array = require( '@stdlib/array/float32' );

var x = new Float32Array( [ 1.0, 9.0, 2.0, 9.0, 3.0, 9.0 ] );

var idx = sindexOfGreaterThanEqualSorted( 3, 2.0, x, 2 );
// returns 1
```

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

<!-- eslint-disable id-length -->

```javascript
var Float32Array = require( '@stdlib/array/float32' );

// Initial array:
var x0 = new Float32Array( [ 0.0, 1.0, 9.0, 2.0, 9.0, 3.0 ] );

// Create an offset view:
var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Find index:
var idx = sindexOfGreaterThanEqualSorted( 3, 2.0, x1, 2 );
// returns 1
```

#### sindexOfGreaterThanEqualSorted.ndarray( N, searchElement, x, strideX, offsetX )

Returns the index of the first element in a sorted single-precision floating-point strided array which is greater than or equal to a specified search element using alternative indexing semantics.

<!-- eslint-disable id-length -->

```javascript
var Float32Array = require( '@stdlib/array/float32' );

var x = new Float32Array( [ 1.0, 2.0, 2.0, 3.0 ] );

var idx = sindexOfGreaterThanEqualSorted.ndarray( x.length, 2.0, x, 1, 0 );
// returns 1
```

The function has the following additional parameters:

- **offsetX**: starting index.

While [`typed array`][mdn-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, to access only the last three elements of the strided array:

<!-- eslint-disable id-length -->

```javascript
var Float32Array = require( '@stdlib/array/float32' );

var x = new Float32Array( [ 9.0, 9.0, 9.0, 1.0, 2.0, 3.0 ] );

var idx = sindexOfGreaterThanEqualSorted.ndarray( 3, 2.0, x, 1, x.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

- The input strided array must be sorted in either **strictly** ascending or descending order.
- If `N <= 0`, both functions return `-1`.
- When comparing elements, both functions use the less-than-or-equal-to operator `<=`. As a consequence, comparisons involving `NaN` always evaluate to `false`, and `-0` and `+0` are considered the same.

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

<!-- eslint-disable id-length -->

```javascript
var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var ssorthp = require( '@stdlib/blas/ext/base/ssorthp' );
var sindexOfGreaterThanEqualSorted = require( '@stdlib/blas/ext/base/sindex-of-greater-than-equal-sorted' );

var x = discreteUniform( 10, -100, 100, {
'dtype': 'float32'
});
ssorthp( x.length, 1, x, 1 );
console.log( x );

var idx = sindexOfGreaterThanEqualSorted( x.length, 0.0, x, 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/sindex_of_greater_than_equal_sorted.h"
```

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

#### stdlib_strided_sindex_of_greater_than_equal_sorted( N, searchElement, \*X, strideX )

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

Returns the index of the first element in a sorted single-precision floating-point strided array which is greater than or equal to a specified search element.

```c
const float x[] = { 1.0f, 2.0f, 2.0f, 3.0f };

int idx = stdlib_strided_sindex_of_greater_than_equal_sorted( 4, 2.0f, x, 1 );
// returns 1

const float y[] = { 3.0f, 2.0f, 2.0f, 1.0f };

idx = stdlib_strided_sindex_of_greater_than_equal_sorted( 4, 2.0f, y, 1 );
// returns 0
```

The function accepts the following arguments:

- **N**: `[in] CBLAS_INT` number of indexed elements.
- **searchElement**: `[in] float` search element.
- **X**: `[in] float*` sorted input array.
- **strideX**: `[in] CBLAS_INT` stride length.

```c
CBLAS_INT stdlib_strided_sindex_of_greater_than_equal_sorted( const CBLAS_INT N, const float searchElement, const float *X, const CBLAS_INT strideX );
```

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

#### stdlib_strided_sindex_of_greater_than_equal_sorted_ndarray( N, searchElement, \*X, strideX, offsetX )

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

Returns the index of the first element in a sorted single-precision floating-point strided array which is greater than or equal to a specified search element using alternative indexing semantics.

```c
const float x[] = { 1.0f, 2.0f, 2.0f, 3.0f };

int idx = stdlib_strided_sindex_of_greater_than_equal_sorted_ndarray( 4, 2.0f, x, 1, 0 );
// returns 1
```

The function accepts the following arguments:

- **N**: `[in] CBLAS_INT` number of indexed elements.
- **searchElement**: `[in] float` search element.
- **X**: `[in] float*` sorted input array.
- **strideX**: `[in] CBLAS_INT` stride length.
- **offsetX**: `[in] CBLAS_INT` starting index.

```c
CBLAS_INT stdlib_strided_sindex_of_greater_than_equal_sorted_ndarray( const CBLAS_INT N, const float searchElement, const float *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );
```

</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">

- The input strided array must be sorted in either **strictly** ascending or descending order.
- If `N <= 0`, both functions return `-1`.

</section>

<!-- /.notes -->

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

<section class="examples">

### Examples

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

int main( void ) {
// Create a sorted strided array:
const float x[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f };

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

// Specify a stride:
const int strideX = 1;

// Perform a search:
int idx = stdlib_strided_sindex_of_greater_than_equal_sorted( N, 4.0f, x, strideX );

// 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/float32]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/float32

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

</section>

<!-- /.links -->
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