alibGetOffsets
For an
n-dimensional array, convert a set of
n-dimensional indices into a set of one-dimensional indices, i.e., convert a set of multidimensional indices into their flat equivalents.
alibIndexNdTo1d and
alibGetOffsets do the same thing but differ in the way the
n-dimensional indices are supplied. For
m conversions,
alibIndexNdTo1d takes
n pointers to
m-element arrays, and
alibGetOffsets takes
m pointers to
n-element arrays.
Prototype
void alibGetOffsets( wvlong n, wvlong *d, wvlong m, wvlong p, wvlong **b, wvlong *i )
Parameters
n — (Input) The number of dimensions for the reference array. This array, possibly virtual, is the array to which the indices refer.
*d — (Input) The n-element array of dimensions for the reference array.
m — (Input) The number of indices to be converted.
p — (Input) The number of coordinates supplied in the set of n-dimensional indices. Normally p = n, but setting p < n lets only the first p coordinates be specified, with the remaining coordinates implicitly assuming the value 0.
**b — (Input) The m-element array of pointers to p-element arrays defining the set of m n-dimensional indices into the reference array.
*i — (Input/Output) The m-element array. On return, i contains the one-dimensional equivalents to the n-dimensional indices b. For a reference array c, the relationship between the sets of indices is:
c[ i[j] ] = c[ b[j][0], ..., b[j][p-1], 0, ..., 0 ]
where if p = n then:
c[ i[j] ] = c[ b[j][0], ..., b[j][n-1] ]
Example
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "alib.h"
void main() { /* array of dimensions to use for two-dimensional,
three-dimensional, and four-dimensional examples */
wvlong dims[4] = {2,2,3,4}; /* make-up coordinates for a pair of points for
two-dimensional, three-dimensional, four-dimensional
examples */
wvlong b2d0[2] = {1,1}; wvlong b2d1[2] = {2,2}; wvlong b3d0[3] = {0,1,1}; wvlong b3d1[3] = {1,2,2}; wvlong b4d0[4] = {0,0,1,1}; wvlong b4d1[4] = {1,1,2,2}; wvlong *b2[2] = {b2d0,b2d1}; wvlong *b3[2] = {b3d0,b3d1}; wvlong *b4[2] = {b4d0,b4d1}; /* make an output array to use for the two-dimensional,
three-dimensional, and four-dimensional examples */
wvlong i[2];
/* just for reference, make some one-dimensional index data \
to use in each example */
UCHAR h[48];
alibinit( NULL, NULL, NULL, NULL );
alibIndexb( 48, 0, 1, h );
printf( "\n\n just for reference, \n" );
printf( " show a (3,4) array initialized with one-dimensional indices" );
alibinit( NULL, NULL, NULL, NULL );
alibPrintArrayb( 1, 1, 3, 4, h, NULL);
printf( "\n\n for a (3,4) reference array, \n" );
printf( " convert the pair of two-dimensional indices b2 into one-dimensional indices \n\n\n" );
alibGetOffsets( 2, &dims[2], 2, 2, b2, i );
printf( "%8lld %8lld\n", i[0], i[1] );
printf( "\n\n just for reference, \n" );
printf( " show a (2,3,4) array initialized with one-dimensional indices" );
alibPrintArrayb( 1, 2, 3, 4, h, NULL);
printf( "\n\n for a (2,3,4) reference array, \n" );
printf( " convert the pair of three-dimensional indices b3 into one-dimensional indices \n\n\n" );
alibGetOffsets( 3, &dims[1], 2, 3, b3, i );
printf( "%8lld %8lld\n", i[0], i[1] );
printf( "\n\n just for reference, \n" );
printf( " show a (2,2,3,4) array initialized with one-dimensional indices" );
alibPrintArrayb( 2, 2, 3, 4, h, NULL);
printf( "\n\n for a (2,2,3,4) reference array, \n" );
printf( " convert the pair of four-dimensional indices b4 into one-dimensional indices \n\n\n" );
alibGetOffsets( 4, dims, 2, 4, b4, i );
printf( "%8lld %8lld\n", i[0], i[1] );
}
Output:
just for reference,
show a (3,4) array initialized with one-dimensional indices
0 1 2 3
4 5 6 7
8 9 10 11
for a (3,4) reference array,
convert the pair of two-dimensional indices b2 into one-dimensional indices
5 10
just for reference,
show a (2,3,4) array initialized with one-dimensional indices
0 1 2 3
4 5 6 7
8 9 10 11
12 13 14 15
16 17 18 19
20 21 22 23
for a (2,3,4) reference array,
convert the pair of three-dimensional indices b3 into one-dimensional indices
5 22
just for reference,
show a (2,2,3,4) array initialized with one-dimensional indices
0 1 2 3
4 5 6 7
8 9 10 11
12 13 14 15
16 17 18 19
20 21 22 23
24 25 26 27
28 29 30 31
32 33 34 35
36 37 38 39
40 41 42 43
44 45 46 47
for a (2,2,3,4) reference array,
convert the pair of four-dimensional indices b4 into one-dimensional indices
5 46
Version 2017.1
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