Re: Each Parallel issue

[rocuinneagain]

m'[x] is not parallel execution

 

There can be cases where the overhead of using multiple threads can make execution slower than single threaded. (.i.e performing many small operations)

.Q.fc is available to help in some of these cases.

https://code.kx.com/q/ref/dotq/#qfc-parallel-on-cut

 

If you measure memory usage with ts note that it only sees usage in main thread. It does not sum usage from all threads. So you cannot compare results directly.

 

q)\ts {til 10000000;x}'[til 1000] // \ts shows real memory usage 
5395 134250848 
q)\ts {til 10000000;x}':[til 1000] // \ts only sees memory usage in main thread - not the sum of threads 
5612 33408

 

q)\ts {x}'[til 100000] // Single core 
8 4746288 

q)\ts {x}':[til 100000] // Slower due to parallel overhead 
13 4194864 

q)\ts .Q.fc[{x}][til 100000] //Faster way to use multiple cores 
1 3146512