5 Replies Latest reply on Sep 22, 2010 4:45 AM by himanshu.gautam

    FCStacks influence on number of wavefronts in-flight

    Raistmer
      what values is too high?

      "
      FCStacks - The number of flow control stack size used by the kernel (only for GPU device). This number may affect the number of wavefronts in-flight. To reduce the stack size, reduce the amount of flow control nesting in the kernel.
      "
      Could someone give some numbers, please. How this number will affect the number of simultaneously executed wavefronts on SIMD ?
      For example one of my kernels has FCStacks ==2, another one FCStacks ==6.
      In what case this number will be limiting factor?

      EDIT: the kernel with FCStacks ==6 has pretty high GPR usage too, 55 GPRs used.
      What will limit number of wavefronts in this case? GPR usage or FCStacks value?
      And how many wavefronts per SIMD I could expect ?