time-to-botec

Benchmark sampling in different programming languages
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main.c (3508B)

      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/vind2bind.h"
     20 #include "stdlib/ndarray/index_modes.h"
     21 #include "stdlib/ndarray/orders.h"
     22 #include <stdint.h>
     23 
     24 /**
     25 * Converts a linear index in an array view to a linear index in an underlying data buffer.
     26 *
     27 * ## Notes
     28 *
     29 * -   In "error" mode, the function returns `-1` if an index is out-of-bounds.
     30 *
     31 * @param ndims    number of dimensions
     32 * @param shape    array shape (dimensions)
     33 * @param strides  array strides
     34 * @param offset   location of the first indexed value **based** on the stride array
     35 * @param order    specifies whether an array is row-major (C-style) or column-major (Fortran-style)
     36 * @param idx      linear index in an array view
     37 * @param mode     specifies how to handle a linear index which exceeds array dimensions
     38 * @return         index
     39 *
     40 * @example
     41 * #include "stdlib/ndarray/base/vind2bind.h"
     42 * #include "stdlib/ndarray/index_modes.h"
     43 * #include "stdlib/ndarray/orders.h"
     44 *
     45 * int64_t ndims = 2;
     46 * int64_t shape[] = { 3, 3 };
     47 * int64_t strides[] = { -3, 1 };
     48 * int64_t offset = 6;
     49 *
     50 * int64_t idx = stdlib_ndarray_vind2bind( ndims, shape, strides, offset, STDLIB_NDARRAY_ROW_MAJOR, 1, STDLIB_NDARRAY_INDEX_ERROR );
     51 * // returns 7
     52 */
     53 int64_t stdlib_ndarray_vind2bind( 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 ) {
     54 	int64_t len;
     55 	int64_t ind;
     56 	int64_t s;
     57 	int64_t i;
     58 
     59 	len = 1;
     60 	for ( i = 0; i < ndims; i++ ) {
     61 		len *= shape[ i ];
     62 	}
     63 	if ( mode == STDLIB_NDARRAY_INDEX_CLAMP ) {
     64 		if ( idx < 0 ) {
     65 			idx = 0;
     66 		} else if ( idx >= len ) {
     67 			idx = len - 1;
     68 		}
     69 	} else if ( mode == STDLIB_NDARRAY_INDEX_WRAP ) {
     70 		if ( idx < 0 ) {
     71 			idx += len; // slight optimization to avoid modulo arithmetic when |idx| <= len
     72 			if ( idx < 0 ) {
     73 				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
     74 				if ( idx != 0 ) {
     75 					idx += len;
     76 				}
     77 			}
     78 		} else if ( idx >= len ) {
     79 			idx -= len; // slight optimization to avoid modulo arithmetic when len < idx <= 2*len
     80 			if ( idx >= len ) {
     81 				idx %= len;
     82 			}
     83 		}
     84 	} else if ( idx < 0 || idx >= len ) {
     85 		return -1;
     86 	}
     87 	// The approach which follows is to resolve a view index to its subscripts and then plug the subscripts into the standard formula for computing the linear index in the underlying data buffer...
     88 	ind = offset;
     89 	if ( order == STDLIB_NDARRAY_COLUMN_MAJOR ) {
     90 		for ( i = 0; i < ndims; i++ ) {
     91 			s = idx % shape[ i ]; // assume nonnegative "shape"
     92 			idx -= s;
     93 			idx /= shape[ i ];
     94 			ind += s * strides[ i ];
     95 		}
     96 		return ind;
     97 	}
     98 	// Case: row-major
     99 	for ( i = ndims-1; i >= 0; i-- ) {
    100 		s = idx % shape[ i ]; // assume nonnegative "shape"
    101 		idx -= s;
    102 		idx /= shape[ i ];
    103 		ind += s * strides[ i ];
    104 	}
    105 	return ind;
    106 }