time-to-botec

Benchmark sampling in different programming languages
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main.c (4518B)

      1 /**
      2 * @license Apache-2.0
      3 *
      4 * Copyright (c) 2018 The Stdlib Authors.
      5 *
      6 * Licensed under the Apache License, Version 2.0 (the "License");
      7 * you may not use this file except in compliance with the License.
      8 * You may obtain a copy of the License at
      9 *
     10 *    http://www.apache.org/licenses/LICENSE-2.0
     11 *
     12 * Unless required by applicable law or agreed to in writing, software
     13 * distributed under the License is distributed on an "AS IS" BASIS,
     14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     15 * See the License for the specific language governing permissions and
     16 * limitations under the License.
     17 */
     18 
     19 #include "stdlib/ndarray/base/ind2sub.h"
     20 #include "stdlib/ndarray/index_modes.h"
     21 #include "stdlib/ndarray/orders.h"
     22 #include <stdint.h>
     23 #include <stdlib.h>
     24 
     25 /**
     26 * Converts a linear index to an array of subscripts.
     27 *
     28 * ## Notes
     29 *
     30 * -   When provided a stride array containing negative strides, if an `offset` is greater than `0`, the function interprets the linear index as an index into the underlying data buffer for the array, thus returning subscripts from the perspective of that buffer. If an `offset` is equal to `0`, the function treats the linear index as an index into an array view, thus returning subscripts from the perspective of that view. In short, from the perspective of a view, view data is always ordered.
     31 *
     32 * -   In "error" mode, the function returns `-1` if an index is out-of-bounds.
     33 *
     34 * @param ndims    number of dimensions
     35 * @param shape    array shape (dimensions)
     36 * @param strides  array strides
     37 * @param offset   location of the first indexed value **based** on the stride array
     38 * @param order    specifies whether an array is row-major (C-style) or column-major (Fortran-style)
     39 * @param idx      linear index in an array view
     40 * @param mode     specifies how to handle a linear index which exceeds array dimensions
     41 * @param out      output array
     42 * @return         status code
     43 *
     44 * @example
     45 * #include "stdlib/ndarray/base/ind2sub.h"
     46 * #include "stdlib/ndarray/index_modes.h"
     47 * #include "stdlib/ndarray/orders.h"
     48 * #include <stdint.h>
     49 *
     50 * int64_t ndims = 2;
     51 * int64_t shape[] = { 3, 3 };
     52 * int64_t strides[] = { -3, 1 };
     53 * int64_t offset = 6;
     54 *
     55 * int64_t out[ 2 ];
     56 *
     57 * int8_t status = stdlib_ndarray_ind2sub( ndims, shape, strides, offset, STDLIB_NDARRAY_ROW_MAJOR, 7, STDLIB_NDARRAY_INDEX_ERROR, out );
     58 * if ( status == -1 ) {
     59 *     // Handle error...
     60 * }
     61 */
     62 int8_t stdlib_ndarray_ind2sub( int64_t ndims, int64_t *shape, int64_t *strides, int64_t offset, enum STDLIB_NDARRAY_ORDER order, int64_t idx, enum STDLIB_NDARRAY_INDEX_MODE mode, int64_t *out ) {
     63 	int64_t len;
     64 	int64_t s;
     65 	int64_t k;
     66 	int64_t i;
     67 
     68 	len = 1;
     69 	for ( i = 0; i < ndims; i++ ) {
     70 		len *= shape[ i ];
     71 	}
     72 	if ( mode == STDLIB_NDARRAY_INDEX_CLAMP ) {
     73 		if ( idx < 0 ) {
     74 			idx = 0;
     75 		} else if ( idx >= len ) {
     76 			idx = len - 1;
     77 		}
     78 	} else if ( mode == STDLIB_NDARRAY_INDEX_WRAP ) {
     79 		if ( idx < 0 ) {
     80 			idx += len; // slight optimization to avoid modulo arithmetic when |idx| <= len
     81 			if ( idx < 0 ) {
     82 				idx -= len*( (int64_t)( idx/len ) ); // this is equivalent to `idx mod len`, where the result has same sign as dividend (i.e., `idx`); cannot use `%` as the sign of the result is implementation defined in C
     83 				if ( idx != 0 ) {
     84 					idx += len;
     85 				}
     86 			}
     87 		} else if ( idx >= len ) {
     88 			idx -= len; // slight optimization to avoid modulo arithmetic when len < idx <= 2*len
     89 			if ( idx >= len ) {
     90 				idx %= len;
     91 			}
     92 		}
     93 	} else if ( idx < 0 || idx >= len ) { // mode == 'error'
     94 		return -1;
     95 	}
     96 	if ( offset == 0 ) {
     97 		if ( order == STDLIB_NDARRAY_COLUMN_MAJOR ) {
     98 			for ( i = 0; i < ndims; i++ ) {
     99 				s = idx % shape[ i ];
    100 				idx -= s;
    101 				idx /= shape[ i ];
    102 				out[ i ] = s;
    103 			}
    104 			return 0;
    105 		}
    106 		// Case: row-major
    107 		for ( i = ndims-1; i >= 0; i-- ) {
    108 			s = idx % shape[ i ];
    109 			idx -= s;
    110 			idx /= shape[ i ];
    111 			out[ i ] = s;
    112 		}
    113 		return 0;
    114 	}
    115 	if ( order == STDLIB_NDARRAY_COLUMN_MAJOR ) {
    116 		for ( i = ndims-1; i >= 0; i-- ) {
    117 			s = strides[ i ];
    118 			if ( s < 0 ) {
    119 				k = idx / s; // truncates
    120 				idx -= k * s;
    121 				out[ i ] = shape[ i ] - 1 + k;
    122 			} else {
    123 				k = idx / s; // cppcheck-suppress zerodivcond // truncates
    124 				idx -= k * s;
    125 				out[ i ] = k;
    126 			}
    127 		}
    128 		return 0;
    129 	}
    130 	// Case: row-major
    131 	for ( i = 0; i < ndims; i++ ) {
    132 		s = strides[ i ];
    133 		if ( s < 0 ) {
    134 			k = idx / s; // truncates
    135 			idx -= k * s;
    136 			out[ i ] = shape[ i ] - 1 + k;
    137 		} else {
    138 			k = idx / s; // cppcheck-suppress zerodivcond // truncates
    139 			idx -= k * s;
    140 			out[ i ] = k;
    141 		}
    142 	}
    143 	return 0;
    144 }