Min and Max View Buffer Indices

Compute the minimum and maximum linear indices in an underlying data buffer which are accessible to an array view.

Usage

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

minmaxViewBufferIndex( shape, strides, offset )

Computes the minimum and maximum linear indices in an underlying data buffer which are 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 = 0;

var idx = minmaxViewBufferIndex( shape, strides, offset );
// returns [ 0, 3 ]

minmaxViewBufferIndex.assign( shape, strides, offset, out )

Computes the minimum and maximum linear indices in an underlying data buffer which are accessible to an array view and assigns results to a provided output array.

var shape = [ 2, 2 ];
var strides = [ -1, -2 ];
var offset = 3;

var out = [ 0, 0 ];
var idx = minmaxViewBufferIndex.assign( shape, strides, offset, out );
// returns [ 0, 3 ]

var bool = ( idx === out );
// returns true

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 minmaxViewBufferIndex = require( '@stdlib/ndarray/base/minmax-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 a view offset

    // Compute the minimum and maximum linear indices:
    idx = minmaxViewBufferIndex( shape, strides, offset );
    console.log( 'Shape: %s. Strides: %s. Offset: %d. Min idx: %d. Max idx: %d.', shape.join( 'x' ), strides.join( ',' ), offset, idx[ 0 ], idx[ 1 ] );
}

C APIs

Usage

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

stdlib_ndarray_minmax_view_buffer_index( ndims, shape, strides, offset, *out )

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

int64_t ndims = 2;
int64_t shape[] = { 10, 10 };
int64_t strides[] = { 10, 1 };
int64_t offset = 0;
int64_t out[ 2 ];

stdlib_ndarray_minmax_view_buffer_index( ndims, shape, strides, offset, out );

int64_t min = out[ 0 ];
// returns 0

int64_t max = out[ 1 ];
// returns 99

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.
out: [out] int64_t* two-element output array.

int8_t stdlib_ndarray_minmax_view_buffer_index( int64_t ndims, int64_t *shape, int64_t *strides, int64_t offset, int64_t *out );

Examples

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

int main( void ) {
    int64_t ndims = 2;
    int64_t shape[] = { 10, 10 };
    int64_t strides[] = { 10, 1 };
    int64_t offset = 0;
    int64_t out[ 2 ];

    stdlib_ndarray_minmax_view_buffer_index( ndims, shape, strides, offset, out );

    printf( "min: %"PRId64"\n", out[ 0 ] );
    printf( "max: %"PRId64"\n", out[ 1 ] );
}