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Altera_Forum
Honored Contributor I
1,040 Views

How to infer BRAM fan-out

I am doing an OpenCL project of vector multiplication of VecA (M * 1) and VecB (1 * N) which produces a matrix MatC (M * N). I want to use a fan-out design which can support a 2-D processing engine array. Can I go like this to infer fan-our? : 

https://alteraforum.com/forum/attachment.php?attachmentid=14222&stc=1  

 

__kernel 

void matMult() { 

 

...... 

# pragma unroll 

for(int x = 0; x < M; x++) {# pragma unroll 

for(int y = 0; y < N; y++) { 

MatC[x][y] += VecA[x] * VecB[y]; 

 

...... 

 

 

 

Any advice would be much appreciated!!
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9 Replies
Altera_Forum
Honored Contributor I
62 Views

You can achieve this type of systolic array design using the autorun kernel type and num_compute_units (Section 2.3 and 2.4 of Intel FPGA SDK for OpenCL Programming Guide). However, I would expect the same thing to be also achievable in a single kernel using loop unrolling, where the local memory buffers are automatically replicated by the compiler.

Altera_Forum
Honored Contributor I
62 Views

Hi, thanks for your reply! Do you know any OpenCL systolic array design examples? (with code)

Altera_Forum
Honored Contributor I
62 Views

There are some small code snippets in Altera's documents in the sections I mentioned above, but other than that, I do not know of any other public code showing the systolic array design.

Altera_Forum
Honored Contributor I
62 Views

Hi, I tried the systolic array and it takes massive amount of BRAM and registesr (mostly for control overhead) which causes my design to be severely memory-bounded. But if I do the fan-out design, the way I unroll the loop cannot work out, it produces wrong output in hardware run. Do you have any idea how the loops should be unrolled?

Altera_Forum
Honored Contributor I
62 Views

 

--- Quote Start ---  

There are some small code snippets in Altera's documents in the sections I mentioned above, but other than that, I do not know of any other public code showing the systolic array design. 

--- Quote End ---  

 

 

Intel's FPGA systolic array example is a controlled material(using public code may not able to get best performance as not optimized for FPGA), and in the event user wish to have a copy that need to contact Altera representative separately. 

 

Regards, 

CloseCL 

(This message was posted on behalf of Intel Corporation)
Altera_Forum
Honored Contributor I
62 Views

Hi, Sir/madam, 

 

may I ask who should I contact if I would like to request for a copy? 

 

Regards, 

Lancer Chiang
Altera_Forum
Honored Contributor I
62 Views

Hi Lancer, 

 

You can contact our sales/FAE as NDA is required. 

 

Thanks, 

 

Regards, 

CloseCL 

(This message was posted on behalf of Intel Corporation)
Altera_Forum
Honored Contributor I
62 Views

Hi Sir/Madam, 

 

Many thanks! Is the copy an OpenCL implementation? 

 

Regards, 

Lancer Chiang
Altera_Forum
Honored Contributor I
62 Views

Do you know any OpenCL systolic array design examples? (with code)

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