improve omp for blocks

4 jobs for master in 8 minutes (queued for 1 minute and 32 seconds)
Status Job ID Name Coverage
  Build
passed #1087
build_debug

00:02:44

passed #1088
build_opt

00:04:01

 
  Test
passed #1089
test_debug

00:00:41

passed #1090
test_opt

00:00:32