When the complexity of env_spec increases, the compilation speed becomes very slow.

[lanchihi]

I would like to ask why, in the implementation of envpool, the definition and implementation of C++ functions are both placed in the .h file instead of being placed in the .h and .cc files respectively. Is there any particular intention behind this implementation? I'm currently facing a very thorny problem. When my env_spec becomes complex, the compilation time becomes extremely long, and the increase in compilation time is not linearly related to the complexity of the spec. Specifically, when the number of actions/states reaches over 300, the compilation time may exceed 10 minutes. Worse still, the compilation of debug may take more than 1 hour.
The following are some compilation time tests I've done:

action nums	31	+60	+100	+200	+300
build time costs	63s	73s	100s	232s	944s
build time increase	0	+13s	+37s	+162s	+881s

I'm not sure if there is a relationship between the excessively long compilation time and putting both the definition and implementation in the .h file.

[lanchihi]

@Trinkle23897 could you help me answer the questions I've encountered? thanks a lot！

[Trinkle23897]

That's because of template class which we can only place it in .h iirc