[CakeML-dev] Let's remove max_app

[Scott Owens]

I should clarify that this is on the clos_stub branch, which I haven’t merged back to master.

Scott

> On 2017/03/07, at 15:00, Scott Owens <S.A.Owens at kent.ac.uk> wrote:
> 
> I’ve just finished the first improvement on reducing the number of stubs. I’d like to see where we are before trying to get further improvements. Can you re-try this, or even better, tell me what you were doing to get these numbers. Can we get anything meaningful without running the bootstrap (and the attendant 2 day wait)? 
> 
> Scott
> 
>> On 2017/03/05, at 08:21, Magnus Myreen <magnus.myreen at gmail.com> wrote:
>> 
>> Hi all,
>> 
>> We should get rid of max_app. Reasons:
>> 
>> 2. The current compilation strategy produces too much stub code in
>>   clos_to_bvl.  If we really must have max_app (I argue below that
>>   we don't), then it should be something like 10 or 15. With the
>>   current compilation strategy, the binary produced for max_app=9 is
>>   176 kb larger than the binary for max_app=3. I wanted to try
>>   compiling with max_app=10, but that was taking more than 5
>>   minutes. Compiling with max_app=3 takes 7 seconds for me. I
>>   believe the slow down in compilation speed with differing max_app
>>   values is caused by the rapid increase in code size (number of
>>   stubs in clos_to_bvl) as max_app gets larger. My measurements
>>   are below while compiling factorial (and the basis library):
>> 
>>     max_app=1:  10.810s  (* very little room for opts in basis *)
>>     max_app=2:  8.724s
>>     max_app=3:  7.872s  (* allows optimisations in basis code *)
>>     max_app=4:  8.935s
>>     max_app=5:  11.608s
>>     max_app=6:  21.771s
>>     max_app=7:  42.932s
>>     max_app=8:  1m24.872s
>>     max_app=9:  3m9.745s
> 
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