Entering a very large number
On 26/03/2018 00:27, Richard Damon wrote:
> On 3/25/18 8:32 AM, bartc wrote:
>> Using CPython on my machine, doing a string to int conversion that
>> specific number took 200 times as long as doing a normal assignment.
>> That conversion took 4 microseconds.
>> Not significant if it's only done once. But it might be executed a
>> million times.
> The other half of that thought is how does the 4 microseconds to create
> the constant compare to the operations USING that number. My guess is
> that for most things the usage will swamp the initialization, even if
> that is somewhat inefficient.
Calling a function that sets up C using 'C = 288714...' on one line, and
that then calculates D=C+C, takes 0.12 seconds to call 1000000 times.
To do D=C*C, takes 2.2 seconds (I've subtracted the function call
overhead of 0.25 seconds; there might not be any function call).
If I instead initialise C using 'C = int("288712...")', then timings
increase as follows:
0.12 => 3.7 seconds
2.2 => 5.9 seconds
So the overhead /can/ be substantial, and /can/ be significant compared
with doing bignum calculations.
Of course, once initialised, C might be used a hundred times, then the
overhead is less significant. But it is not small enough to just dismiss.