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
48
49
50
51
52
53
54
55
56
57
|
function I = subsindex (G)
%SUBSINDEX subscript index from a GraphBLAS matrix.
% I = subsindex (G) is an overloaded method used when the GraphBLAS
% matrix G is used to index into a non-GraphBLAS matrix A, for A(G).
%
% See also GrB/subsref, GrB/subsasgn.
% SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2022, All Rights Reserved.
% SPDX-License-Identifier: Apache-2.0
% On input, G must contain integers in the range 1 to prod (size (A))-1.
% The dimensions of A are not provided to subsindex.
G = G.opaque ;
% As an extension to the expression A(G), prune zeros and negative
% values first. The expression A(G) becomes A (G (find (G > 0))).
G = gbselect ('>0', G) ;
[m, n, type] = gbsize (G) ;
if (isinteger (m))
% G is so huge that gbsize returns m and n as int64. This means
% that m or n (or both) are bigger than flintmax, so G cannot be full.
G_is_full = false ;
else
G_is_full = (m*n == gbnvals (G)) ;
end
if (isequal (type, 'double') || isequal (type, 'single'))
% double or single: convert to int64
I = gbextractvalues (G) ;
if (~isequal (I, round (I)))
error ('GrB:error', 'array indices must be integers') ;
end
I = int64 (I) ;
elseif (gb_contains (type, 'int'))
% any integer: just extract the values
I = gbextractvalues (G) ;
else
% logical or complex
error ('GrB:error', 'array indices must be integers') ;
end
% I must contain entries in range 0 to prod (size (A)) - 1,
% so subtract the offset
I = I - 1 ;
% reshape I as needed
if (m == 1)
% I should be a row vector instead
I = I' ;
elseif (n > 1 && G_is_full)
% I is should be an m-by-n matrix, so reshape it. But I cannot be
% reshaped to m-by-n if G is sparse, so leave it as a column vector.
I = reshape (I, m, n) ;
end
|
