k-mer algorithms: Compare and Swap

Dr. Rob Edwards from San Diego State University describes how the compare and swap algorithm works. This is widely used in counting k-mers since it provides a lock-free hashing method.

[@leol5910]

Nice explanation

[@oladipotimothy6007]

Nice approach

[@pdaae]

thanks!

[@lucasqwert1]

Why does every thread wait for the log? Thanks !

[@stefansilverio245]

why do we return the "current_value" regardless of whether or not we reset the value at "location"? Wouldn't we want to return the value at "location" if we updated it?

[@leakaufmann9500]

I think that the returned value is used to check that the CAS operation succeeded (current_value == old_value).

[@kkiranayb]

Is data structures finished here ???? Sir

[@chronewhite4197]

I need more explanation, because I don't have much knowledge
How is CAS atomic? There are multiple operations in the title itself - read, compare and set new value

[@sas1one]

At hardware level (Intel CPU) there is an atomic instruction for the compare-and-exchange operation.
INSTRUCTION SET REFERENCE, A-L, 3-208 Vol. 2A
"CMPXCHG-Compare and Exchange"
part of
Intel® 64 and IA-32 Architectures Software Developer’s Manual
Volume 2 (2A, 2B, 2C, & 2D): Instruction Set Reference, A-Z.

[@shivangisingh2643]

my whole attention was on how this amazing person is writing backwards/mirrored (whatever it is called). Good explanation though.

[@kumarprakash8260]

He's not🤣

[@ericfricke4512]

He writes forwards facing us, and then it is mirrored in processing afterwards to compensate.

[@Coder_Minds]

Is this good playlist