multithreading - Is there an advantage of recycling threads -

in c++, want create algorithms following structure:

• a sequential part
• a parallel part a
• a sequential part
• a parallel part b
• a sequential part

using pthreads, can think of 2 ways solve problem:

1. create n threads part , destructing these threads after part finished. allocating n new threads part b.
2. using same threads part , part b using various kinds of synchronization methods available.

how overhead take create new threads solution 1 when performance matters. should go solution 1 or solution 2?

parallel frameworks such openmp recycle threads. called thread pool, , can find information on site. here's 1 related post: thread pool vs thread spawning

if you're concerned performance, best way find out suits application try both approaches , measure them.

in general, if processing task expensive , code easier understand if spawn new threads, that.

and colour argument little, check out post answered using experimentation other day: why 50 threads faster 4?