Contents
Basic operations
Define two int64 arrays
a = int64(1:10)' b = int64(-5:4)'
a =
1
2
3
4
5
6
7
8
9
10
b =
-5
-4
-3
-2
-1
0
1
2
3
4
Test addition
a+b
ans =
-4
-2
0
2
4
6
8
10
12
14
Every operation also works with scalar values
a+1
ans =
2
3
4
5
6
7
8
9
10
11
Test subtraction
a-b
ans =
6
6
6
6
6
6
6
6
6
6
Test multiplication
a.*b
ans =
-5
-8
-9
-8
-5
0
7
16
27
40
Test division and absolute value
a./ (abs(b) + 1)
ans =
0
0
0
1
2
6
3
2
2
2
Powers
int64(2)^50
ans =
1125899906842624
Test modulo
mod(a,2)
ans =
1
2
3
4
5
6
7
8
9
10
Bitshift
bitshift(int64(1),40)
ans =
1099511627776
Matrix multiplication
Matrix multiplication is also supported
A = int64(100*rand(5)) B = int64(100*rand(5,3)) C = A*B Cdouble = double(A)*double(B)
A =
91 34 5 85 69
49 42 22 83 65
79 41 79 8 27
91 96 18 48 0
86 41 5 35 45
B =
94 73 21
30 38 17
41 55 86
14 1 46
56 3 96
C =
14833 8502 13453
11570 6661 13693
13519 11759 12110
12844 11329 7299
12529 8281 8863
Cdouble =
14833 8502 13453
11570 6661 13693
13519 11759 12110
12844 11329 7299
12529 8281 8863
Timing
Generate large matrices
A = int64(100*rand(400)); B = int64(100*rand(400));
Time the multiplication using int64
tic C = A*B; toc
Elapsed time is 0.343107 seconds.
Now try using double instead
A = double(A); B = double(B); tic C = A*B; toc
Elapsed time is 0.017866 seconds.
We see that using doubles is faster for big matrices, because it uses LAPACK, which is heavily optimized.