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function w = GB_spec_reduce_to_vector (w, mask, accum, reduce, A, descriptor)
%GB_SPEC_REDUCE_TO_VECTOR a MATLAB mimic of GrB_reduce (to vector)
%
% Usage:
% w = GB_spec_reduce_to_vector (w, mask, accum, reduce, A, desc)
%
% Reduces a matrix to a vector
% SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2020, All Rights Reserved.
% http://suitesparse.com See GraphBLAS/Doc/License.txt for license.
%-------------------------------------------------------------------------------
% get inputs
%-------------------------------------------------------------------------------
if (nargout > 1 || nargin ~= 6)
error ...
('usage: c = GB_spec_reduce_to_vector (w, mask, accum, reduce, A, desc)') ;
end
% get the class of A
if (isstruct (A))
aclass = A.class ;
else
aclass = GB_spec_type (A) ;
end
% get the reduce operator. default type is the type of A
if (isempty (reduce))
reduce = 'plus'
end
[reduce_op reduce_class] = GB_spec_operator (reduce, aclass) ;
% get the identity
identity = GB_spec_identity (reduce_op, reduce_class) ;
if (isempty (identity))
identity = 0 ;
end
% get the input matrix
A = GB_spec_matrix (A, identity) ;
% get the input vector
w = GB_spec_matrix (w, identity) ;
% get the mask
[C_replace Mask_comp Atrans Btrans Mask_struct] = ...
GB_spec_descriptor (descriptor) ;
mask = GB_spec_getmask (mask, Mask_struct) ;
%-------------------------------------------------------------------------------
% do the work via a clean MATLAB interpretation of the entire GraphBLAS spec
%-------------------------------------------------------------------------------
% apply the descriptor to A
if (Atrans)
A.matrix = A.matrix.' ;
A.pattern = A.pattern' ;
end
tclass = reduce_class ;
[m n] = size (A.matrix) ;
T.matrix = GB_spec_zeros ([m 1], tclass) ;
T.pattern = zeros (m, 1, 'logical') ;
T.matrix (:,:) = identity ;
T.class = tclass ;
% cast A to the type of the reduce operator, but only entries in the pattern
% Note that GraphBLAS does not need the identity value to do this step.
% Nor is the identity value specified in the GraphBLAS spec.
% It is needed here since T is a dense column, not sparse, and the
% implicit values need to be inserted properly.
for i = 1:m
t = identity ;
for j = 1:n
if (A.pattern (i,j))
aij = GB_mex_cast (A.matrix (i,j), reduce_class) ;
t = GB_spec_op (reduce, t, aij) ;
T.pattern (i) = true ;
end
end
T.matrix (i) = t ;
end
%-------------------------------------------------------------------------------
% apply the mask and accum
%-------------------------------------------------------------------------------
% w<mask> = accum (C,T): apply the accum, then mask, and return the result
w = GB_spec_accum_mask (w, mask, accum, T, C_replace, Mask_comp, identity) ;
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