7 ms·

I don't think it's the best code I've ever seen, but a lot of these are surface-level complaints. > * goto inside 3 nested for-loops. C has no pattern for bre

• messe 6y ago
  > C has no pattern for breaking out of multiple for loops at the same time. Other languages like Java and JavaScript introduced "break label;" to handle this edge case. goto is perfectly acceptable to break out of multiple loops. Yeah, that's not what it does. The code looks like this: if (pgeom->Intersect(pentlist[i]->m_parts[j].pPhysGeomProxy->pGeom, gwd,gwd+1, &ip, pcontacts)) { got_unproj: if (dirUnproj.len2()==0) dirUnproj = pcontacts[0].dir; t = pcontacts[0].t; // lock should be released after reading t return t; } for(int ipart=1;ipart<m_nParts;ipart++) if (m_parts[ipart].flagsCollider & pentlist[i]->m_parts[j].flags) { gwd[2].R = Matrix33(qrot); gwd[2].offset = pos + qrot*m_parts[ipart].pos; gwd[2].scale = m_parts[ipart].scale; gwd[2].v = -dirUnproj; if (m_parts[ipart].pPhysGeomProxy->pGeom->Intersect(pentlist[i]->m_parts[j].pPhysGeomProxy->pGeom, gwd+2,gwd+1, &ip, pcontacts)) goto got_unproj; } } Notice (a) the if statement on the same line as the for loop, and (b) the fact that the goto jumps out of a conditional inside a for loop inside of a conditional into a conditional just before the for loop. EDIT: Just realised the poster is referring to a different function. IMO this one is more horrifying.
  • Jasper_ 6y ago
    That's in a different function, so I wasn't counting it, but sure. I mean, I would write it differently, but it's fairly readable. It's jumping to a common function epilogue once it finds something it can collide with. Seriously -- try reading through it rather than gawking at the goto.
    • naikrovek 6y ago
      It's funny watching people reply to you without knowing anything about your skill set and experience. Jasper_ is the real deal, people.
      • iforgotpassword 6y ago
        I still don't know who he is, but just from the arguments brought up you can tell this guy has experience in this stuff. Those blanket statements like "never use goto" and "always trust stl" generally make me wary. I started out with gwbasic once, writing horrible goto spaghetti code. When moving through Pascal and C I eventually learned the "never use goto" mantra and naively tried to follow it at all cost. After I while I eventually encountered the "breaking out of nested loops" problem and refrained from using goto since I didn't want to look like a complete dork. I think I ended up with a flag that was set in the inner loop and checked in the outer and a break in each loop. That's what you get from blindly following rules that others try to present you as god-given.
        • teawrecks 6y ago
          IMO it should be clear from the top of a for loop how many iterations it will run. A goto randomly inside the loop is akin to a side effect in a function. Sure it might be the easiest solution you can think of, and might even generate optimal code, but it's less readable and forces future maintainers to exert more effort to understand the code.
          • iforgotpassword 6y ago
• Hydraulix989 6y ago
  I've found that a lot of more junior engineers just want to rotely pattern match on one-size-fits-all "style" rules in their code review without fully understanding why those rules exist in the first place. Like all rules, there's always exceptions. In a hot code path like the physics engine logic, you're going for performance optimizations (which often LOOK messy) and that means making slight compromises on readability. It's quite a bit different than the code implementing the business logic in your SaaS company.
• jfkebwjsbx 6y ago
  > C has no pattern for breaking out of multiple for loops at the same time. True, but it is cleaner to reorganize the code into several functions and use the return value to propagate across layers if needed. Performance should be the same. > it's not applicable here Why? If there is a new/delete pair anywhere, it should have been an object. > Game developers have a long-seated distrust of std::vector, and for good reasons. Which reasons? std::vector (and std::unique_ptr) is universally useful (unlike many other std data structures) and codegen should be on par as a new/delete pair. If the std is completely broken in some of the console platforms they need to support (likely from what I hear here) then it can also be done with a custom heap array wrapper. So I don’t see the reason why that shouldn’t have been an object.
  • Jasper_ 6y ago
    > True, but it is cleaner to reorganize the code into several functions and use the return value to propagate across layers if needed. I disagree. Having to jump to another function definition which is inline is a bigger mental block than following a goto. The large amount of arguments you'd need to pass might also be a barrier, as is the mental overhead of checking to see if this function might be called from elsewhere. But reasonable people can disagree on this point. I suggest you try to clean up the function yourself and see if your function-ed version is in any way improved. > Why? If there is a new/delete pair anywhere, it should have been an object. The case we want is that we have a large array of pairwise collisions. This is a temporary array used inside the method. If we ever have more than this, we need a new (contiguous) array. Are you suggesting that the code should have done something like this? template<typename T> class TempArray { T* storage; void resize(int n) { delete[] storage; storage = new T[n]; }; I mean, sure, it's a very minor cleanup. It changes like, two lines though, and makes us have to access the array through an awkward ->storage pointer. Not ideal IMO. > codegen should be on par as a new/delete pair. Here's modern MSVC. Let's play "spot the difference": https://gcc.godbolt.org/z/KqR-LN https://gcc.godbolt.org/z/KqR-LN I'm not even doing anything but allocating the vector / array. It took me 2 minutes to navigate to godbolt and type this in. Don't just say "should be"... test it yourself!
    • Remnant44 6y ago