Issue1388 (#1389)
* Calculation of chunk range limits was ignoring num_cpu
bug introduced by me in #1262 - should fix #1388
* Calculation of range limits was ignoring num_cpu
bug introduced by me in #1262
* Calculation of chunk range limits was ignoring num_cpu
bug introduced by me in #1262
* Calculation of chunk range limits was ignoring num_cpu
bug introduced by me in #1262
* Calculation of chunk range limits was ignoring num_cpu
bug introduced by me in #1262
* Calculation of chunk range limits was ignoring num_cpu
bug introduced by me in #1262