feat: add C implementation for stats/base/ndarray/sstdev by aryan7071 · Pull Request #14718 · stdlib-js/stdlib

aryan7071 · 2026-08-27T17:46:03Z

Resolves a part of #14034

Description

What is the purpose of this pull request?

This pull request:

adds a native C implementation for computing the standard deviation of a one-dimensional single-precision floating-point ndarray (sstdev).
adds the required native addon build configuration, C source files, headers, and JavaScript bindings.
updates the test suite and benchmarks to cover and utilize the new native C addon.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

[RFC] : add C implementations for @stdlib/stats/base/ndarray packages (tracking issue) #14034

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Read, understood, and followed the contributing guidelines.

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stdlib-bot · 2026-08-28T20:29:49Z

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/ndarray/sstdev	$\\color{green}203/203$ $\\color{green}+0.00\\%$	$\\color{green}7/7$ $\\color{green}+0.00\\%$	$\\color{green}2/2$ $\\color{green}+0.00\\%$	$\\color{green}203/203$ $\\color{green}+0.00\\%$

The above coverage report was generated for the changes in this PR.

…stdev

ujjwalv01 · 2026-09-05T10:46:58Z

Please update the require statement in benchmark.js to point to the main package export './../lib/main.js' instead of './../lib/' so that the benchmark correctly tests the main entry point.

ujjwalv01 · 2026-09-05T10:47:29Z

+/**
+* Computes the standard deviation of a one-dimensional single-precision floating-point ndarray.
+*
+* @param arrays    list containing an input ndarray and a zero-dimensional ndarray specifying the degrees of freedom adjustment


Suggested change

* @param arrays list containing an input ndarray and a zero-dimensional ndarray specifying the degrees of freedom adjustment

* ## Notes

*

* - The function expects the following ndarrays:

*

* - a one-dimensional input ndarray.

* - a zero-dimensional ndarray specifying the degrees of freedom adjustment.

*

* @param arrays list containing ndarrays

ujjwalv01 · 2026-09-05T10:47:37Z

+*/
+float stdlib_stats_sstdev( const struct ndarray *arrays[] ) {
+	const struct ndarray *x = arrays[ 0 ];
+	const struct ndarray *correction = arrays[ 1 ];


Suggested change

const struct ndarray *correction = arrays[ 1 ];

ujjwalv01 · 2026-09-05T10:47:40Z

+	const struct ndarray *x = arrays[ 0 ];
+	const struct ndarray *correction = arrays[ 1 ];
+
+	float c;


Suggested change

float c;

float correction;

stdlib_ndarray_get_float32( arrays[ 1 ], NULL, &correction );

ujjwalv01 · 2026-09-05T10:47:45Z

+	// For zero-dimensional arrays, `stdlib_ndarray_iget_float32` returns the first (and only) indexed element, regardless of the supplied index:
+	stdlib_ndarray_iget_float32( correction, 0, &c );
+
+	return API_SUFFIX(stdlib_strided_sstdev_ndarray)( stdlib_ndarray_dimension( x, 0 ), c, (const float *)stdlib_ndarray_data( x ), stdlib_ndarray_stride_elements( x, 0 ), stdlib_ndarray_offset_elements( x ) );


Suggested change

return API_SUFFIX(stdlib_strided_sstdev_ndarray)( stdlib_ndarray_dimension( x, 0 ), c, (const float *)stdlib_ndarray_data( x ), stdlib_ndarray_stride_elements( x, 0 ), stdlib_ndarray_offset_elements( x ) );

return API_SUFFIX(stdlib_strided_sstdev_ndarray)( stdlib_ndarray_dimension( x, 0 ), correction, (const float *)stdlib_ndarray_data( x ), stdlib_ndarray_stride_elements( x, 0 ), stdlib_ndarray_offset_elements( x ) );

ujjwalv01 · 2026-09-05T10:47:51Z

The test/test.js file should only test the dynamic dispatcher (using proxyquire to mock tryRequire), rather than running the mathematical tests. The actual correctness tests should live exclusively in test.main.js (for JS) and test.native.js (for C).

Right now, test.js is just a copy of test.main.js. Please update test/test.js so it matches the dispatcher testing pattern;

refer this : lib/node_modules/%40stdlib/stats/base/ndarray/dstdev/test/test.js

ujjwalv01 · 2026-09-05T10:48:02Z

+tape( 'the function calculates the standard deviation of a one-dimensional ndarray', opts, function test( t ) {
+	var correction;
+	var expected;
+	var optsD;


Suggested change

var optsD;

var opts;

ujjwalv01 · 2026-09-05T10:48:03Z

+
+	optsD = {
+		'dtype': 'float32'
+	};


Suggested change

};

opts = {

'dtype': 'float32'

};

ujjwalv01 · 2026-09-05T10:48:07Z

+	};
+
+	x = new Float32Array( [ 1.0, -2.0, -4.0, 5.0, 0.0, 3.0 ] );
+	correction = scalar2ndarray( 1.0, optsD );


Suggested change

correction = scalar2ndarray( 1.0, optsD );

correction = scalar2ndarray( 1.0, opts );

ujjwalv01 · 2026-09-05T10:48:19Z

The local dtype options variable is named optsD throughout this file , please rename it to opts (consistent with the established convention) across all test callbacks.

ujjwalv01 · 2026-09-05T11:03:23Z

@aryan7071 , It looks like lib/index.js was missed in this PR. Since you're adding native C bindings, you need to update lib/index.js to dynamically dispatch to the native implementation (using tryRequire) ,. Please apply the standard tryRequire dispatcher block in lib/index.js;

ujjwalv01 · 2026-09-05T11:03:38Z

Left few suggestions;

aryan7071 · 2026-09-06T15:04:18Z

Hi @ujjwalv01 , thanks for the detailed review! I've pushed a fix commit addressing all of these:

src/main.c: Simplified as suggested removed the intermediate correction ndarray variable and switched to stdlib_ndarray_get_float32( arrays[ 1 ], NULL, &correction ), and added the ## Notes block documenting the expected ndarrays list.
lib/index.js: Added the missing native-fallback dispatcher (tryRequire block) this was indeed missed.
test/test.js: Rewritten to test only the dispatcher logic via proxyquire, matching dstdev's pattern. The actual correctness tests now live exclusively in test.main.js and test.native.js.
test/test.native.js: Renamed optsD → opts throughout for consistency.
benchmark/benchmark.js: Fixed the require path to './../lib/main.js'.

All three test files pass locally (test.js 4/4, test.main.js 12/12, test.native.js 12/12) and the addon rebuilds cleanly.

…stdev

ujjwalv01 · 2026-09-06T15:20:48Z

Looks good to me. Thanks @aryan7071 , for the changes;

cc : @kgryte

0PrashantYadav0

Please add backticks around the package path in the PR title (feat: add C implementation for stats/base/ndarray/sstdev) and fill in the AI disclosure, which still says {{TODO: add disclosure if applicable}}.

0PrashantYadav0 · 2026-10-10T05:13:55Z

+// Create an input ndarray:
+const float xbuf[] = { 1.0f, 2.0f, 3.0f, 4.0f };
+int64_t xshape[] = { 4 };
+int64_t xstrides[] = { STDLIB_NDARRAY_FLOAT32_BYTES_PER_ELEMENT };
+int8_t submodes[] = { STDLIB_NDARRAY_INDEX_ERROR };
+
+struct ndarray *x = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)xbuf, 1, xshape, xstrides, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 1, submodes );
+
+// Create a zero-dimensional ndarray specifying the degrees of freedom adjustment:
+const float cbuf[] = { 1.0f };
+int64_t cshape[] = {};
+int64_t cstrides[] = { 0 };
+
+struct ndarray *correction = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)cbuf, 0, cshape, cstrides, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 0, submodes );
+
+// Compute the standard deviation:
+const struct ndarray *arrays[] = { x, correction };
+float v = stdlib_stats_sstdev( arrays );
+// returns ~2.0817
+
+// Free allocated memory:
+stdlib_ndarray_free( x );
+stdlib_ndarray_free( correction );


Suggested change

// Create an input ndarray:

const float xbuf[] = { 1.0f, 2.0f, 3.0f, 4.0f };

int64_t xshape[] = { 4 };

int64_t xstrides[] = { STDLIB_NDARRAY_FLOAT32_BYTES_PER_ELEMENT };

int8_t submodes[] = { STDLIB_NDARRAY_INDEX_ERROR };

struct ndarray *x = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)xbuf, 1, xshape, xstrides, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 1, submodes );

// Create a zero-dimensional ndarray specifying the degrees of freedom adjustment:

const float cbuf[] = { 1.0f };

int64_t cshape[] = {};

int64_t cstrides[] = { 0 };

struct ndarray *correction = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)cbuf, 0, cshape, cstrides, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 0, submodes );

// Compute the standard deviation:

const struct ndarray *arrays[] = { x, correction };

float v = stdlib_stats_sstdev( arrays );

// returns ~2.0817

// Free allocated memory:

stdlib_ndarray_free( x );

stdlib_ndarray_free( correction );

// Create an ndarray:

const float data[] = { 1.0f, -2.0f, 2.0f };

int64_t shape[] = { 3 };

int64_t strides[] = { STDLIB_NDARRAY_FLOAT32_BYTES_PER_ELEMENT };

int8_t submodes[] = { STDLIB_NDARRAY_INDEX_ERROR };

struct ndarray *x = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)data, 1, shape, strides, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 1, submodes );

// Create an ndarray for specifying the degrees of freedom adjustment:

const float cdata[] = { 1.0f };

int64_t cstrides[] = { 0 };

struct ndarray *corr = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)cdata, 0, NULL, cstrides, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 1, submodes );

// Compute the result:

const struct ndarray *arrays[] = { x, corr };

float v = stdlib_stats_sstdev( arrays );

// returns ~2.0817

// Free allocated memory:

stdlib_ndarray_free( x );

stdlib_ndarray_free( corr );

With { 1, 2, 3, 4 } this snippet returns 1.290994, not ~2.0817 (compiled and ran it). int64_t cshape[] = {} is also not valid C99 (-pedantic: "zero size arrays are an extension"). Match svariancech/README.md.

0PrashantYadav0 · 2026-10-10T05:13:55Z

+
+The function accepts the following arguments:
+
+-   **arrays**: `[in] struct ndarray**` list containing the following ndarrays: a one-dimensional input ndarray and a zero-dimensional ndarray specifying the degrees of freedom adjustment.


Suggested change

- **arrays**: `[in] struct ndarray**` list containing the following ndarrays: a one-dimensional input ndarray and a zero-dimensional ndarray specifying the degrees of freedom adjustment.

- **arrays**: `[in] struct ndarray**` list containing the following ndarrays:

- `[in] struct ndarray*` a one-dimensional input ndarray.

- `[in] struct ndarray*` a zero-dimensional ndarray specifying the degrees of freedom adjustment. Providing a non-zero degrees of freedom adjustment has the effect of adjusting the divisor during the calculation of the [standard deviation][standard-deviation] according to `N-c` where `N` is the number of elements in the input ndarray and `c` corresponds to the provided degrees of freedom adjustment. When computing the [standard deviation][standard-deviation] of a population, setting this parameter to `0` is the standard choice (i.e., the provided array contains data constituting an entire population). When computing the corrected sample [standard deviation][standard-deviation], setting this parameter to `1` is the standard choice (i.e., the provided array contains data sampled from a larger population; this is commonly referred to as Bessel's correction).

Match dstdev/README.md.

0PrashantYadav0 · 2026-10-10T05:13:55Z

+	// Create a zero-dimensional ndarray specifying the degrees of freedom adjustment:
+	const float cbuf[] = { 1.0f };
+	int64_t *cshape = NULL;
+	int64_t cstrides[] = { 0 };
+
+	// cppcheck-suppress invalidPointerCast
+	struct ndarray *correction = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)cbuf, 0, cshape, cstrides, offset, order, imode, 0, submodes );


Suggested change

// Create a zero-dimensional ndarray specifying the degrees of freedom adjustment:

const float cbuf[] = { 1.0f };

int64_t *cshape = NULL;

int64_t cstrides[] = { 0 };

// cppcheck-suppress invalidPointerCast

struct ndarray *correction = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)cbuf, 0, cshape, cstrides, offset, order, imode, 0, submodes );

// Create a data buffer for an ndarray specifying the degrees of freedom adjustment:

const float cbuf[] = { 1.0f };

// Specify the array strides:

int64_t cstrides[] = { 0 };

// Create an ndarray for the degrees of freedom adjustment:

// cppcheck-suppress invalidPointerCast

struct ndarray *correction = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT32, (uint8_t *)cbuf, 0, NULL, cstrides, 0, order, imode, nsubmodes, submodes );

The correction ndarray shouldn't reuse x's offset; match svariancech/examples/c/example.c. Same in README.md:301-306 and benchmark/c/benchmark.length.c:141-144.

0PrashantYadav0 · 2026-10-10T05:13:55Z

+* Generates a random number on the interval [0, 1).
+*
+* @return random number
+*/
+static double rand_double( void ) {
+	return (double)rand() / ( (double)RAND_MAX + 1.0 );


Suggested change

* Generates a random number on the interval [0, 1).

*

* @return random number

*/

static double rand_double( void ) {

return (double)rand() / ( (double)RAND_MAX + 1.0 );

* Generates a random number on the interval [0,1).

*

* @return random number

*/

static float rand_float( void ) {

int r = rand();

return (float)r / ( (float)RAND_MAX + 1.0f );

Line 135 then becomes data[ i ] = ( rand_float() * 20000.0f ) - 10000.0f;. See #15170 (comment) and svariancech/benchmark/c/benchmark.length.c.

0PrashantYadav0 · 2026-10-10T05:13:55Z

+	$(QUIET) $(CC) $(CFLAGS) $(fPIC) $(INCLUDE) -o $@ $(SOURCE_FILES) $< $(LIBPATH) -lm $(LIBRARIES)
+
+#/
+# Runs compiled examples.


Suggested change

# Runs compiled examples.

# Runs compiled benchmarks.

0PrashantYadav0 · 2026-10-10T05:13:56Z

+	// Create a const-qualified view of the argument pointer list:
+	const struct ndarray *arr[ 2 ] = {
+		arrays[ 0 ],
+		arrays[ 1 ]
+	};
+	// Perform computation:
+	STDLIB_NAPI_CREATE_DOUBLE( env, (double)stdlib_stats_sstdev( arr ), v );
+
+	// Free allocated memory:
+	stdlib_ndarray_free( arrays[ 0 ] );
+	arrays[ 0 ] = NULL;
+
+	stdlib_ndarray_free( arrays[ 1 ] );
+	arrays[ 1 ] = NULL;


Suggested change

// Create a const-qualified view of the argument pointer list:

const struct ndarray *arr[ 2 ] = {

arrays[ 0 ],

arrays[ 1 ]

};

// Perform computation:

STDLIB_NAPI_CREATE_DOUBLE( env, (double)stdlib_stats_sstdev( arr ), v );

// Free allocated memory:

stdlib_ndarray_free( arrays[ 0 ] );

arrays[ 0 ] = NULL;

stdlib_ndarray_free( arrays[ 1 ] );

arrays[ 1 ] = NULL;

// Create a const-qualified view of the argument pointer list:

const struct ndarray *arr[ 2 ] = { arrays[ 0 ], arrays[ 1 ] };

// Perform computation:

STDLIB_NAPI_CREATE_DOUBLE( env, (double)stdlib_stats_sstdev( arr ), v );

// Free allocated memory:

stdlib_ndarray_free( arrays[ 0 ] );

stdlib_ndarray_free( arrays[ 1 ] );

arrays[ 0 ] = NULL;

arrays[ 1 ] = NULL;

Match svariancech/src/addon.c.

0PrashantYadav0 · 2026-10-10T05:13:56Z

+* var opts = {
 *     'dtype': 'float32'
-* });
+* };
+*
+* var x = new Float32Vector( [ 1.0, -2.0, 2.0 ] );
+*
+* var correction = scalar2ndarray( 1.0, opts );


Suggested change

* var opts = {

* 'dtype': 'float32'

* });

* };

*

* var x = new Float32Vector( [ 1.0, -2.0, 2.0 ] );

*

* var correction = scalar2ndarray( 1.0, opts );

* var x = new Float32Vector( [ 1.0, -2.0, 2.0 ] );

* var correction = scalar2ndarray( 1.0, {

* 'dtype': 'float32'

* });

This change isn't needed; keep the example as in lib/main.js. Same in lib/native.js:48-54, see #15170 (comment).

feat: add C implementation for sstdev

78e9936

aryan7071 requested a review from a team August 27, 2026 17:46

stdlib-bot added Statistics Issue or pull request related to statistical functionality. Needs Review A pull request which needs code review. and removed Needs Review A pull request which needs code review. labels Aug 27, 2026

aryan7071 marked this pull request as draft August 28, 2026 09:59

stdlib-bot removed the Needs Review A pull request which needs code review. label Aug 28, 2026

fix: add missing manifest.json for stats/base/ndarray/sstdev

88579b8

aryan7071 added 2 commits August 28, 2026 16:16

benchmark and example corrected makefil

68c24ce

fix: correct 0-d ndarray shape handling and benchmark Makefile target

197d858

aryan7071 marked this pull request as ready for review August 29, 2026 21:48

Merge branch 'develop' into add-c-implementation-stats-base-ndarray-s…

37c1d13

…stdev

stdlib-bot added the Needs Review A pull request which needs code review. label Aug 29, 2026

ujjwalv01 mentioned this pull request Aug 30, 2026

[RFC] : add C implementations for @stdlib/stats/base/ndarray packages (tracking issue) #14034

Open

ujjwalv01 reviewed Sep 5, 2026

View reviewed changes

fix: address review feedback for sstdev

53c0d33

Merge branch 'develop' into add-c-implementation-stats-base-ndarray-s…

ae4ae7a

…stdev

ujjwalv01 mentioned this pull request Sep 7, 2026

feat: add C implementation for stats/base/ndarray/sstdevch #14815

Open

6 of 7 tasks

0PrashantYadav0 suggested changes Oct 10, 2026

View reviewed changes

-* @param arrays    list containing an input ndarray and a zero-dimensional ndarray specifying the degrees of freedom adjustment
+* ## Notes
+*
+* -   The function expects the following ndarrays:
+*
+*     -   a one-dimensional input ndarray.
+*     -   a zero-dimensional ndarray specifying the degrees of freedom adjustment.
+*
+* @param arrays    list containing ndarrays

	float c;
	float correction;
	stdlib_ndarray_get_float32( arrays[ 1 ], NULL, &correction );

	return API_SUFFIX(stdlib_strided_sstdev_ndarray)( stdlib_ndarray_dimension( x, 0 ), c, (const float *)stdlib_ndarray_data( x ), stdlib_ndarray_stride_elements( x, 0 ), stdlib_ndarray_offset_elements( x ) );
	return API_SUFFIX(stdlib_strided_sstdev_ndarray)( stdlib_ndarray_dimension( x, 0 ), correction, (const float *)stdlib_ndarray_data( x ), stdlib_ndarray_stride_elements( x, 0 ), stdlib_ndarray_offset_elements( x ) );

	correction = scalar2ndarray( 1.0, optsD );
	correction = scalar2ndarray( 1.0, opts );


		The function accepts the following arguments:

		- arrays: `[in] struct ndarray**` list containing the following ndarrays: a one-dimensional input ndarray and a zero-dimensional ndarray specifying the degrees of freedom adjustment.

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aryan7071 commented Aug 27, 2026

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