[GAP Forum] a problem

[Stefan Kohl]

Dear Forum,

Vivek Jain asked:

How can I know the time requirement of that a particular program/code  which
> I prepare to run in gap?
>
> Also can I know how much memory will be needed to run a particular code?
>

This depends on what you want to do and what you know about your code and
the
algorithms or methods you use. -- Due to the algorithmic unsolvability of
the halting
problem for Turing machines, there is no algorithm to make such predictions.
This
is nothing GAP-specific, but holds for programs in any programming language
which
permits emulating Turing machines.

If you in fact rather want to know afterwards how long the execution of a
particular code
has taken, you can use

1. the variable `time', whose value is the runtime of the last command in an
interactive
    GAP session in milliseconds,
2. the function `Runtime', which returns the machine time spent so far in
the present
    GAP session, and
3. the function `Runtimes', which returns a record containing more detailed
information,
    see ?Runtimes.

Apart from this, GAP also provides profiling facilities - see ?Profiling.

You can determine the amount of memory used by a given GAP object by the
operation
`MemoryUsage'. Also, you can obtain information related to garbage
collections and the
present size of the GAP workspace -- see ?GasmanStatistics,
?GasmanMessageStatus
and ?GasmanLimits. Independent of this, on most machines, you can determine
the size
of the GAP job by means of the operating system.

Best regards,

    Stefan Kohl