complexity of `entries` grows quadratically in number of rows

[mahrud]

I did not expect this:

i1 : elapsedTime H = random(ZZ^200000, ZZ^10);
 -- 1.75006s elapsed

              200000       10
o1 : Matrix ZZ       <-- ZZ

i5 : elapsedTime entries H^{0..10000};
 -- 1.87336s elapsed

i6 : elapsedTime entries H^{0..20000};
 -- 7.24654s elapsed

i7 : elapsedTime entries H^{0..30000};
 -- 41.3092s elapsed

i8 : elapsedTime flatten apply(3, i -> entries H^{i*10000..(i+1)*10000-1});
 -- 7.09806s elapsed

In particular, this seems to be about number of rows only:

i14 : elapsedTime H = transpose H;
 -- .277403s elapsed

               10       200000
o14 : Matrix ZZ   <-- ZZ

i15 : elapsedTime entries H;
 -- 2.09016s elapsed

[mahrud]

XD

i1 : elapsedTime H = random(ZZ^200000, ZZ^10);
 -- 1.59819s elapsed

              200000       10
o1 : Matrix ZZ       <-- ZZ

i2 : elapsedTime transpose entries transpose H;
 -- 2.64812s elapsed