Dear Daniel,
On Nov 2, 5:12 pm, Daniel Allcock <[EMAIL PROTECTED]> wrote:
> Hi all, just got started with SAGE and I hope someone has a suggestion
> for me. I have a .sage file defining a big list of approx 170,000 4x4
> matrices with rational number entries, which I will want SAGE to do
> various things to. It takes SAGE 4-5 minutes to read in the file
> (which was produced by a C++ program), and surely this can be
> improved.
Of course, without seeing the code I have no clear idea why this takes
so long and blows up the memory. But one remark: There are different
ways to create a matrix over QQ, and they do not all take the same
time.
Examples:
sage: timeit('M=Matrix([[1/2,2/3],[3/4,4/5]])')
625 loops, best of 3: 212 µs per loop
sage: timeit('M=Matrix(QQ,
2,2);M[0,0]=1/2;M[0,1]=2/3;M[1,0]=3/4;M[1,1]=4/5')
625 loops, best of 3: 111 µs per loop
sage: MS=MatrixSpace(QQ,2,2)
sage: timeit('M=MS(1/2,2/3,3/4,4/5)')
625 loops, best of 3: 70.4 µs per loop
Cheers
Simon
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