Re: efficiency

[Ray Andrews <rayandrews@eastlink.ca>]

On 04/02/17 08:47 AM, Peter Stephenson wrote:
> On Sat, 04 Feb 2017 08:38:52 -0800
> Ray Andrews <rayandrews@eastlink.ca> wrote:
>> Of course.  Still it's good to understand the theory of the thing. As I
>> said, in practice the difference was a milisecond but I backed the wrong
>> horse, which is instructive since it suggests that the shell likes fewer
>> lines more than it likes simplified calculation.
> Yes, that does sound right.  In an interpreted language quite a lot of
> the overhead is that you need to start from scratch on each line of
> input, working out what it is and passing through the hierarchy first of
> parsing and then execution.  The math expression is interpreted, too,
> and has its own parsing and execution phases, but in a significantly
> more limited way.  The actual time taken adding, subtracting and
> dividing to do the calculation within that is utterly trivial,
> I should think nearer nanoseconds than microseconds.

But the microseconds were for the entire function to execute several 
times, which is far more than just the math.
>
> pws
>
Excellent, that's my lesson.