minViewBufferIndex

Compute the minimum linear index in an underlying data buffer accessible to an array view.

Usage

var minViewBufferIndex = require( '@stdlib/ndarray/base/min-view-buffer-index' );

minViewBufferIndex( shape, strides, offset )

Computes the minimum linear index in an underlying data buffer accessible to an array view.

// Array shape:
var shape = [ 2, 2 ];

// Stride array:
var strides = [ -2, -1 ];

// Index offset which specifies the location of the first indexed value:
var offset = 13; // includes a view offset

var idx = minViewBufferIndex( shape, strides, offset );
// returns 10

Examples

var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
var shape2strides = require( '@stdlib/ndarray/base/shape2strides' );
var strides2offset = require( '@stdlib/ndarray/base/strides2offset' );
var randu = require( '@stdlib/random/base/randu' );
var minViewBufferIndex = require( '@stdlib/ndarray/base/min-view-buffer-index' );

var strides;
var offset;
var shape;
var idx;
var i;
var j;

shape = [ 0, 0, 0 ];

for ( i = 0; i < 100; i++ ) {
    // Generate a random array shape:
    shape[ 0 ] = discreteUniform( 1, 10 );
    shape[ 1 ] = discreteUniform( 1, 10 );
    shape[ 2 ] = discreteUniform( 1, 10 );

    // Generate strides:
    if ( randu() < 0.5 ) {
        strides = shape2strides( shape, 'row-major' );
    } else {
        strides = shape2strides( shape, 'column-major' );
    }
    j = discreteUniform( 0, shape.length-1 );
    strides[ j ] *= ( randu() < 0.5 ) ? -1 : 1;

    // Compute the index offset:
    offset = strides2offset( shape, strides ) + 25; // include view offset

    // Compute the minimum linear index:
    idx = minViewBufferIndex( shape, strides, offset );
    console.log( 'Shape: %s. Strides: %s. Offset: %d. Min idx: %d.', shape.join( 'x' ), strides.join( ',' ), offset, idx );
}

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C APIs

Usage

#include "stdlib/ndarray/base/min_view_buffer_index.h"

stdlib_ndarray_min_view_buffer_index( ndims, *shape, *strides, offset )

Computes the minimum linear index (in bytes) in an underlying data buffer accessible to an array view.

#include <stdint.h>

int64_t ndims = 2;
int64_t shape[] = { 10, 10 };
int64_t strides[] = { 10, 1 };
int64_t offset = 10;

int64_t idx = stdlib_ndarray_min_view_buffer_index( ndims, shape, strides, offset );
// returns 10

The function accepts the following arguments:

• ndims: [in] int64_t number of dimensions.
• shape: [in] int64_t* array shape (dimensions).
• strides: [in] int64_t* array strides (in bytes).
• offset: [in] int64_t index offset.

int64_t stdlib_ndarray_min_view_buffer_index( const int64_t ndims, const int64_t *shape, const int64_t *strides, const int64_t offset );

Examples

#include "stdlib/ndarray/base/min_view_buffer_index.h"
#include <stdint.h>
#include <stdio.h>
#include <inttypes.h>

int main( void ) {
    // Specify the number of dimensions:
    const int64_t ndims = 2;

    // Define an array shape:
    const int64_t shape[] = { 10, 10 };

    // Define array strides:
    const int64_t strides[] = { -2, 5 };

    // Define an offset:
    const int64_t offset = 100;

    // Compute the minimum accessible index:
    int64_t idx = stdlib_ndarray_min_view_buffer_index( ndims, shape, strides, offset );

    // Print the results:
    printf( "idx: %"PRId64"\n", idx );
}