avoid multiple redefinition

[MitchellX]

By including these guards, you ensure that if ops.h is included multiple times in different files, its contents will only be processed once by the compiler, avoiding redefinition errors and saving time

[simon-mo]

thank you for your contribution! can you check is this the case for all other header files

[WoosukKwon]

@MitchellX Thanks for the PR! As Simon mentioned, it seems there are several header files that do not have the guards. Could you please add the guards to all theses header files?

[MitchellX]

@simon-mo @WoosukKwon Sure, I'll do it later.

[WoosukKwon]

@MitchellX Are you still working on this PR?

[MitchellX]

@WoosukKwon My apologies for the oversight. I was so overwhelmed the last few weeks, forgetting to modify the head files. Yes, I'm still working on a vllm related project, and I can help address this issue on Saturday.

[WoosukKwon]

@MitchellX I see. Thanks for letting us know. In this case, can I directly modify this PR to accelerate the process? I think we got your point and just needed to add #pragma once to other header files. I can take this if you are ok with it.

[MitchellX]

@WoosukKwon Sure, do as you wish.

[WoosukKwon]

LGTM. Thanks for pointing this out!