On May 29, 7:29 am, Emil <emi...@gmail.com> wrote:
> On 29 May 2012 15:21, William Stein <wst...@gmail.com> wrote:
>
> > Can you give an example? E.g., a matrix and a random seed?
>
> Not easily... If it is really necessary I can find the matrix that it
> failed on. Although most of the time it works on this matrix...
That would be of great help. It's usually easier to *set* the seed
than to get it after the fact, since there is a lot of state to
capture. What one would usually do for something like this is:
set_random_seed(0)
while true:
do_operation_that occasionally_gives_an_error()
i.e., if you can whittle it down to a test where the error occurs
after reasonable time, debugging can already start. For added value,
experiment with setting a different value in set_random_seed so that
the error occurs sooner. In principle one should be able to do
while true:
C=current_randstate()
do_operation()
but you'll in fact be getting the same object every time. Only the
seed originally used is accessible. Good random number generators keep
track of a lot more internal state and in sage there are several.
Another alternative would be
for seedvalue in range(10^8):
print "trying seed: ",seedvalue
with seed(seedvalue):
do_random_error_prone_operation()
In all cases, you're hoping that these "seed" routines indeed set all
relevant random generators. Since there are many doctests in sage that
depend on the same, there's a good chance they do.
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