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function test40
%TEST40 test GrB_Matrix_extractElement
% SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2022, All Rights Reserved.
% SPDX-License-Identifier: Apache-2.0
fprintf ('\n ------ quick test of GrB_Matrix_extractElement\n') ;
Prob = ssget (936) ;
A = Prob.A ;
[m n] = size (A) ;
for i = double (1:500:m)
for j = double (1:500:n)
x1 = full (A (i,j)) ;
use_scalar = (rand (1) > 0.5) ;
x2 = GB_mex_Matrix_extractElement (A, uint64 (i-1), uint64 (j-1), '', use_scalar) ;
assert (isequal (x1,x2)) ;
end
end
i2 = double (1:10:m) ;
j2 = double (1:10:n) ;
ni = length (i2) * length (j2) ;
I = zeros (ni, 1) ;
J = zeros (ni, 1) ;
X = zeros (ni, 1) ;
k = 0 ;
for i = i2
for j = j2
k = k + 1 ;
I (k) = i ;
J (k) = j ;
end
end
% loop 1
tic
for i = i2
for j = j2
x1 = full (A (i,j)) ;
end
end
t1 = toc ;
fprintf ('built-in, scalar A(i,j): %g sec\n', t1) ;
% loop 2 is about the same speed
tic
for k = 1:ni
X (k) = full (A (I (k), J (k))) ;
end
t2 = toc ;
fprintf ('built-in, scalar A(i,j): %g sec (2nd loop)\n', t2) ;
t0 = min (t1, t2) ;
I = uint64 (I-1) ;
J = uint64 (J-1) ;
X1 = zeros (ni, 1) ;
tic
for k = 1:ni
use_scalar = (rand (1) > 0.5) ;
X1 (k) = GB_mex_Matrix_extractElement (A, I (k), J (k), '', use_scalar) ;
end
t3 = toc ;
fprintf ('GrB single A(i,j): %g sec speedup: %g\n', t3, t0/ t3) ;
% This is about 15x faster than built-in loop 1 and 2.
% the loop is internal in the mexFunction, so this code
% avoids the interpretive overhead. It also avoids the
% malloc need to construct the GraphBLAS header for
% the shallow copy of A, and the malloc for the scalar result,
% for each iteration. Instead, those mallocs are done once.
tic
X2 = GB_mex_Matrix_extractElement (A, I, J) ;
t4 = toc ;
fprintf ('GrB many A(i,j): %g sec speedup: %g\n', t4, t0/ t4) ;
assert (isequal (X, X2)) ;
assert (isequal (X, X1)) ;
X2 = GB_mex_Matrix_extractElement (A, I, J, '', true) ;
assert (isequal (X, X2)) ;
tic
[I,J,X] = find (A) ;
t7 = toc ;
fprintf ('built-in, [I,J,X] = find(A) %g sec\n', t7) ;
tic
[I2, J2, X2] = GB_mex_extractTuples (A) ;
t8 = toc ;
fprintf ('GrB [I,J,X] = find(A) %g sec, speedup %g\n', t8, t7/t8) ;
assert (isequal (I, double (I2+1)))
assert (isequal (J, double (J2+1)))
assert (isequal (X, X2))
ni = length (I) ;
% built-in loop 3
tic
for k = 1:ni
X (k) = full (A (I (k), J (k))) ;
end
t5 = toc ;
fprintf ('built-in, scalar A(i,j): %g sec (all entries)\n', t5) ;
tic
X2 = GB_mex_Matrix_extractElement (A, I2, J2) ;
t6 = toc ;
fprintf ('GrB many A(i,j): %g sec (all entries) speedup: %g\n', t6, t5/ t6) ;
assert (isequal (X, X2)) ;
X2 = GB_mex_Matrix_extractElement (A, I2, J2, '', true) ;
assert (isequal (X, X2)) ;
%-------------------------------------------------------------------------------
% vector
V = A (:) ;
mn = length (V) ;
for i = double (1:500:mn)
x1 = full (V (i)) ;
x2 = GB_mex_Vector_extractElement (V, uint64 (i-1)) ;
assert (isequal (x1,x2)) ;
end
tic
[I,J,X] = find (V) ;
t9 = toc ;
fprintf ('built-in, [I,J,X] = find(V) %g sec\n', t9) ;
ni = length (I) ;
tic
[I2, J2, X2] = GB_mex_extractTuples (V) ;
t8 = toc ;
fprintf ('GrB [I,J,X] = find(V) %g sec, speedup %g\n', t8, t7/t8) ;
assert (isequal (I, double (I2+1)))
assert (isequal (J, double (J2+1)))
assert (isequal (X, X2))
% built-in vector loop
tic
for k = 1:ni
X (k) = full (V (I (k))) ;
end
t10 = toc ;
fprintf ('built-in, scalar V(i): %g sec (all entries)\n', t10) ;
tic
X2 = GB_mex_Vector_extractElement (V, I2) ;
t6 = toc ;
fprintf ('GrB many A(i,j): %g sec (all entries) speedup: %g\n', t6, t5/ t6) ;
assert (isequal (X, X2)) ;
fprintf ('\ntest40: all tests passed\n') ;
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