Re: Small grammar, long compilation time

On 2017-10-30 16:05, Larry Evans wrote:
> On 10/30/2017 09:28 AM, Søren Enevoldsen wrote:
> [snip]
>> I submitted a pull request with some strings that should parse ok 
>> (they do here). 
> Thanks :)
>> I had to turn off BOOST_SPIRIT_X3_DEBUG in order to compile the code 
>> in the link you sent.
> That's strange.  I just compiled&ran without problem, and it showed
> the output of the debug trace, part of which is:

I think the debug flag not working might have been my fault. I noticed I 
was on develop in your fix-repo, and the pulls updated get_rhs, so I 
switched and I can compile with the debug #define enabled now. I no 
longer need: -DBOOST_SPIRIT_ATTR_XFORM_IN_RULE=0 
-DBOOST_SPIRIT_GET_RHS_CRTP=1 anymore.

> --{--cut here--
>> /home/evansl/dwnlds/llvm/5.0/prebuilt/clang+llvm-5.0.0-linux-x86_64-ubuntu16.04/bin/clang++ 
>> -c -O0 -gdwarf-2 -stdlib=libc++  -std=c++1z 
>> -ftemplate-backtrace-limit=0 -fdiagnostics-show-template-tree 
>> -fno-elide-type -fmacro-backtrace-limit=0 
>> -I/home/evansl/prog_dev/boost/releases/ro/boost_1_65_1/sandbox/pull_requests/context_debug_fix.fork/spirit/include 
>> -I/home/evansl/prog_dev/boost/releases/ro/boost_1_65_1 
>> -I/home/evansl/prog_dev/boost/sandbox/lje/non_variadic_templates 
>> -DBOOST_SPIRIT_X3_EXPERIMENTAL_GET_RHS_NS=1 
>> -DBOOST_SPIRIT_X3_EXPERIMENTAL_GET_RHS_CRTP=0 
>> -DBOOST_SPIRIT_X3_EXPERIMENTAL_ATTR_XFORM_IN_RULE=1 
>> -ftemplate-depth=200  wccs_parser.cpp -MMD -o 
>> /tmp/build/clangxx5_0_pkg/boost/releases/ro/boost_1_65_1/sandbox/pull_requests/context_debug_fix.fork/spirit/workbench/x3/rec_ex_orig/wccs_parser.o 
>> /home/evansl/dwnlds/llvm/5.0/prebuilt/clang+llvm-5.0.0-linux-x86_64-ubuntu16.04/bin/clang++ 
>> -stdlib=libc++ 
>> /tmp/build/clangxx5_0_pkg/boost/releases/ro/boost_1_65_1/sandbox/pull_requests/context_debug_fix.fork/spirit/workbench/x3/rec_ex_orig/wccs_parser.o 
>> -o 
>> /tmp/build/clangxx5_0_pkg/boost/releases/ro/boost_1_65_1/sandbox/pull_requests/context_debug_fix.fork/spirit/workbench/x3/rec_ex_orig/wccs_parser.exe
>> /tmp/build/clangxx5_0_pkg/boost/releases/ro/boost_1_65_1/sandbox/pull_requests/context_debug_fix.fork/spirit/workbench/x3/rec_ex_orig/wccs_parser.exe 
>> <process>
>>   <try>0</try>
>>   <choice>
>>     <try>0</try>
>>     <composition>
>>       <try>0</try>
>>       <actionPrefix>
>>         <try>0</try>
>>         <N11wccs_parser22AstActionPrefixProcessE>
>>           <try>0</try>
>>           <N11wccs_parser9AstActionE>
>>             <try>0</try>
>>             <fail/>
>>           </N11wccs_parser9AstActionE>
>>           <fail/>
>>         </N11wccs_parser22AstActionPrefixProcessE>
>>         <renaming>
>>           <try>0</try>
>>           <restriction>
>>             <try>0</try>
>>             <primitive>
>>               <try>0</try>
>>               <N11wccs_parser14AstNullProcessE>
>>                 <try>0</try>
>>
>
> --}--cut here--
>
> Hence, I'm guessing I've not pushed on my local changes to the 
> remote.  I'll
> try to figure out what and correct.
> [snip]
>>
>> But just to be clear, it is compilation time that is the problem, not 
>> any particular input string. 
>
> I understand.  However, I wanted to see it actually run.  In addition,
> I wanted to see the changes I just made, worked. That's one reason for
> the #define BOOST_SPIRIT_X3_DEBUG.
>
>> I have been trying to simplify the case. Whenever I eliminate a rule 
>> in the "tower"/hierarchy of rules Process ::= choice and choice -> 
>> composition -> renaming -> restriction -> primitive, where we have 
>> the rule Process ::= choice again in parenthesis, the compilation 
>> time becomes practical again. I would assume such a hierarchy is not 
>> unusual for expressions. A naive guess is that it is somehow 
>> connected to the use of AstAnyProcess and the x3::forward_ast. But I 
>> have been unable to simplify the grammar without unexploding the 
>> compile time.
>
> Thanks for trying.  This make me suspect that this is an important test
> case because still, despite hours trying to understand and modify the
> code, I'm still don't understand it very well.  I suspect pinning down
> why this is happening my help me (and others) understand the code 
> better.  Of course 2 eyes on the problem is more helpful than just
> one; so, I hope you keep trying with me to understand the root cause
> of this problem.

My knowledge of Spirit is limited to that of an extremely recent user, 
and I do know really know how the template magic happens. But, I am 
certainly willing to help from my side, if able.



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