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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.

-->

# gfirstIndexGreaterThanEqual

> Return the index of the first element in a strided array which is greater than or equal to a corresponding element in another 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

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

```javascript
var gfirstIndexGreaterThanEqual = require( '@stdlib/blas/ext/base/gfirst-index-greater-than-equal' );
```

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

Returns the index of the first element in a strided array which is greater than or equal to a corresponding element in another strided array.

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

```javascript
var x = [ 1.0, 2.0, 3.0, 4.0 ];
var y = [ 2.0, 2.0, 2.0, 2.0 ];

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

The function has the following parameters:

- **N**: number of indexed elements.
- **x**: first input array.
- **strideX**: stride length for `x`.
- **y**: second input array.
- **strideY**: stride length for `y`.

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

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

```javascript
var x = [ 1.0, 2.0, 3.0, 4.0 ];
var y = [ 5.0, 6.0, 7.0, 8.0 ];

var idx = gfirstIndexGreaterThanEqual( 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:

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

```javascript
var x = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ];
var y = [ 9.0, 9.0, 0.0, 9.0, 9.0, 9.0 ];

var idx = gfirstIndexGreaterThanEqual( 3, x, 2, y, 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 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, 9.0, 0.0, 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 = gfirstIndexGreaterThanEqual( 2, x1, 1, y1, 1 );
// returns 1
```

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

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

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

Returns the index of the first element in a strided array which is greater than or equal to a corresponding element in another strided array using alternative indexing semantics.

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

```javascript
var x = [ 1.0, 2.0, 3.0, 4.0 ];
var y = [ 2.0, 2.0, 2.0, 2.0 ];

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

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 id-length, max-len -->

```javascript
var x = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ];
var y = [ 9.0, 9.0, 9.0, 0.0, 9.0, 9.0 ];

var idx = gfirstIndexGreaterThanEqual.ndarray( 3, x, 1, x.length-3, y, 1, y.length-3 );
// returns 0
```

</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 greater than or equal to a corresponding element in `y` using the greater-than-or-equal operator `>=`. As a consequence, comparisons involving `NaN` always evaluate to `false`, and `-0` and `+0` are considered the same.
- Both functions support array-like objects having getter and setter accessors for array element access (e.g., [`@stdlib/array/base/accessor`][@stdlib/array/base/accessor]).

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

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

```javascript
var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var gfirstIndexGreaterThanEqual = require( '@stdlib/blas/ext/base/gfirst-index-greater-than-equal' );

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

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

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

</section>

<!-- /.examples -->

<!-- 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">

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

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

</section>

<!-- /.links -->
Original file line number Diff line number Diff line change
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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.
*/

'use strict';

// MODULES //

var bench = require( '@stdlib/bench' );
var pow = require( '@stdlib/math/base/special/pow' );
var isInteger = require( '@stdlib/assert/is-integer' ).isPrimitive;
var zeros = require( '@stdlib/array/zeros' );
var ones = require( '@stdlib/array/ones' );
var format = require( '@stdlib/string/format' );
var pkg = require( './../package.json' ).name;
var gfirstIndexGreaterThanEqual = require( './../lib' ); // eslint-disable-line id-length


// FUNCTIONS //

/**
* Creates a benchmark function.
*
* @private
* @param {PositiveInteger} len - array length
* @returns {Function} benchmark function
*/
function createBenchmark( len ) {
var x = zeros( len, 'float64' );
var y = ones( len, 'float64' );
return benchmark;

/**
* Benchmark function.
*
* @private
* @param {Benchmark} b - benchmark instance
*/
function benchmark( b ) {
var out;
var i;

b.tic();
for ( i = 0; i < b.iterations; i++ ) {
out = gfirstIndexGreaterThanEqual( x.length, x, 1, y, 1 );
if ( out !== out ) {
b.fail( 'should return an integer' );
}
}
b.toc();
if ( !isInteger( out ) ) {
b.fail( 'should return an integer' );
}
b.pass( 'benchmark finished' );
b.end();
}
}


// MAIN //

/**
* Main execution sequence.
*
* @private
*/
function main() {
var len;
var min;
var max;
var f;
var i;

min = 1; // 10^min
max = 6; // 10^max

for ( i = min; i <= max; i++ ) {
len = pow( 10, i );

f = createBenchmark( len );
bench( format( '%s:len=%d', pkg, len ), f );
}
}

main();
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