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UDLContext uses incorrect data type to store blob
gino0
Join Date: 26 May 19
Posts: 12
Posted: Mon, 2019-07-01 23:26
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I am using SNPE 1.27.1.382 and I am following the UDL tutorial https://developer.qualcomm.com/docs/snpe/udl_tutorial.html.

I am experiencing a problem with packing and unpacking the blob data. On the Python converter side, I am packing 4-byte integers, which could result in packing "0x00" bytes (for example, 5 is packed as \x05\x00\x00\x00). 

self._blob  # 112\x00\x18\x00\x02\x00\x02\x00\x00\x00\x04\x00\x00\x00\x00\x01\x00\x00\x80...

This seems to be a problem on the runtime side, because the UDLContext class (include/zdl/DlSystem/UDLContext.hpp) seems to store the blob as a std::string, which truncates on `0x00` bytes. So the data received on the UDL factory callback is already truncated. 

const void *blob = c->getBlob();     # c.m_Buffer = "112"
const int blobSize = c->getSize();   # c.m_Size = 3
The UDLContext object stores the blob as std::string, which truncates on the 4th byte \x00. The resulting m_Size(blob.size()) is now only 3, and then UDLContext initializes m_Buffer by copying m_Size bytes from the blob. So only the first 3 bytes are copied. The rest of the data is not copied over to m_Buffer. All of the UDL callbacks then become useless because the rest of the blob data is missing.
 
Here is the code for the UDLContext.hpp constructor:
 
UDLContext(const std::string& name,
           const std::string& type,
           int32_t id,
           const std::string& blob) :
    m_Name(name), m_Type(type), m_Size(blob.size()), m_Id(id) {
    std::cout << blob << std::endl;
    // FIXME not dealing with alloc error
    m_Buffer = new uint8_t[m_Size];
    std::memcpy(m_Buffer, blob.data(), m_Size);
}
 
Notice that blob is a std::string and that m_Buffer allocation is based on string.size which truncates on null characters.
 
Am I missing something here? 
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Re: UDLContext uses incorrect data type to store blob
gino0
Join Date: 26 May 19
Posts: 12
Posted: Wed, 2019-07-03 00:30
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The issue is reproducible with the sample UDL codes from the tutorial.

  • $SNPE_ROOT/examples/Python/UdlExample
  • $SNPE_ROOT/examples/NativeCpp/UdlExample

 

The blob size returned by snpe-dlc-info and by the UDLContext is 1 (which is because the layer type is \x01\x00\x00\x00).

This is different from what is displayed on the tutorial where the blob size is 2017.

 

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Re: UDLContext uses incorrect data type to store blob
luochenchi
Join Date: 3 Aug 17
Posts: 1
Posted: Tue, 2019-07-09 20:30
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This problem exists since 1.25. The last working UDL version is 1.24. Interestingly, 'include/zdl/DlSystem/UDLContext.hpp' has not changed from 1.24 and 1.25. Hope, SNPE team come up and fix it. Your offical UDL example is NOT working.

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Re: UDLContext uses incorrect data type to store blob
gino0
Join Date: 26 May 19
Posts: 12
Posted: Wed, 2019-07-10 02:45
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The problem is indeed fixed by using an older SNPE, specifically 1.24.0.256.  

The blob size and contents are now correct.

You can download the older version from here: https://developer.qualcomm.com/downloads/neural-processing-sdk-ai-v1240?...

Do not use 1.25, 1.26, and 1.27 if you want to use UDLs.

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