3 ms·

absolutely. Few years ago i got back deep into C++ after 18 years of mostly Java, and i'm amazed, it is like travel back in time - we (a large C++ platform) are

by trhway 6y ago

absolutely. Few years ago i got back deep into C++ after 18 years of mostly Java, and i'm amazed, it is like travel back in time - we (a large C++ platform) are looping over vectors instead of using hashtables/maps, copying strings all the time (we have 4 major types of strings plus some minor ones), and don't get me started on multithreading and locking/synchronization - such an easy and natural thing in Java - even these days the people in C++ world is still seem to be hesitant to use locking and as result of that hesitance push themselves into a myriad of multithreading issues when they risk and/or are forced to use threads. It a sight to behold when a customer waits for that one core/thread to finish the operation on a 400 core 16TB RAM machine - if it were Java all the 400 cores would be burning, the performance would still feel kind of so-so, and the customer would be building up the nerve to upgrade to 800 core 32 TB :) >pointer indirection 30+ years ago, a student at University, i loved how pointers allowed to code algorithms efficiently and expressively compare to the non-pointer languages of the time. In the industry today the situation is completely opposite as correctly noted by the parent.

bluGill 6y ago
In many cases n is small enough that looping over a vector is faster than a hash lookup. The vector loop is very ry cache friendly, while the hash lookup typically involves a cache miss or two.
- trhway 6y ago
  it would be for a vector where values are stored in the vector entries. Instead it is usually pointers to strings or objects. So you pull from memory by pointer (i.e. cache unfriendly) every string, compare, etc... And small n is usually small until customer actually generates couple orders of magnitude more of those objects than it was in test/dev :)

3 ms·

absolutely. Few years ago i got back deep into C++ after 18 years of mostly Java, and i'm amazed, it is like travel back in time - we (a large C++ platform) are

by trhway 6y ago

bluGill 6y ago
In many cases n is small enough that looping over a vector is faster than a hash lookup. The vector loop is very ry cache friendly, while the hash lookup typically involves a cache miss or two.
- trhway 6y ago
  it would be for a vector where values are stored in the vector entries. Instead it is usually pointers to strings or objects. So you pull from memory by pointer (i.e. cache unfriendly) every string, compare, etc... And small n is usually small until customer actually generates couple orders of magnitude more of those objects than it was in test/dev :)