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benedetto73
Adventurer
Adventurer
332 Views
Registered: ‎09-30-2019

independent function calls not parallelized

I have 8 calls to the same functions (functionX in the code below) on different inputs (and different ports).
Each parameter is connected to its respective HBM bank.

I would expect Vitis to parallelize them all, instead they run 2 at the time.
Even if I use function instantiate and actually get 8 different hw functions, they still run 2 at the time.

I removed some global variables (static constants) that were used across the functions.
My assumption is that there's some dependencies that I am not seeing.
What can I do to uncover those?


C++ kernel on Vitis targeting Alveo U280, HW Emu, linux Ubuntu.
Pseudo code below.


void functionX(B512 *hbm, uint32 size, char zzz)
{
#pragma HLS function_instantiate variable=zzz
...
}

typedef ap_uint<512> B512;
void kernel(B512 *hbm0, B512 *hbm1, ... , B512 *hbm15, uint32 size)
{

#pragma HLS INTERFACE m_axi port = hbm0 offset = slave bundle = hbm0
#pragma HLS INTERFACE s_axilite port = hbm0 bundle = control
...
#pragma HLS INTERFACE m_axi port = hbm15 offset = slave bundle = hbm15
#pragma HLS INTERFACE s_axilite port = hbm15 bundle = control

   preprocessBank(hbm0, hbm4, hbm5);   
   preprocessBank(hbm1, hbm6, hbm7);   
   preprocessBank(hbm2, hbm8, hbm9);   
   preprocessBank(hbm3, hbm10, hbm11);

   functionX(hbm4, size, 1);
   functionX(hbm5, size, 2);
   functionX(hbm6, size, 3);
   functionX(hbm7, size, 4);
   functionX(hbm8, size, 5);
   functionX(hbm9, size, 6);
   functionX(hbm10, size, 7);
   functionX(hbm11, size, 8);
}

 

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2not8.png
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benedetto73
Adventurer
Adventurer
280 Views
Registered: ‎09-30-2019

After lots of attempts I finally got the tool to generate parallel functions.
The key change was to put each of those 8 functions in 8 different namespaces.

However the question why they weren't parallelized is still open.

More generally, my question is:  what are the tools or steps we have to check to make sure whether functions are dependent?

parallel.png
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