[Feature]: 如何看到SPU DeviceObject的具体shares的值？

[wangmn-cufe]

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这里似乎给出了使用secretflow看到SPU DeviceObject具体shares值的方法：#908
但是在不使用secretflow而仅仅使用spu的情况下，如何获取secret shares的值？

我参照https://github.com/secretflow/spu/blob/main/spu/tests/spu_io_test.py
写了如下代码：
import spu.api as ppapi
import spu.spu_pb2 as spu_pb2

def _bytes_to_pb(msg: bytes):...与spu_io_test.py中函数定义相同

config = spu_pb2.RuntimeConfig(
protocol=spu_pb2.ProtocolKind.REF2K,
field=spu_pb2.FieldType.FM64,
fxp_fraction_bits=18,
share_max_chunk_size=4,
)
wsize=2
io = ppapi.Io(wsize, config)

x = np.random.randint(10, size=())
xs = io.make_shares(x, spu_pb2.Visibility.VIS_SECRET)
print(_bytes_to_pb(xs[0].meta))
print(xs[0].share_chunks)
print(xs[1].share_chunks)
print(x)

执行后的结果为：
data_type: DT_I64
visibility: VIS_SECRET
storage_type: "ref2k.Sec"

[b'\x08\x08\x1a\x04\x07\x00\x00\x00', b'\x08\x08\x10\x04\x1a\x04\x00\x00\x00\x00']
[b'\x08\x08\x1a\x04\x07\x00\x00\x00', b'\x08\x08\x10\x04\x1a\x04\x00\x00\x00\x00']
7
请问哪一项是secret shares？或者需要用到其他的函数？

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[w-gc]

print(xs[0].share_chunks)
print(xs[1].share_chunks)

这两个都是secret shares，因为你使用的是"ref2k.Sec"，每方的数据都是一样的（code ref）。另外，在c++转python过程中，会对spu::Value序列化成protobuf，因此输出的结果不可读，具体的逻辑可以看MakeShares。你可以尝试使用Reconstruct对其反序列化。

[wangmn-cufe]

谢谢，参考您的建议和代码ValueChunkProto、heu.py后，在本问题所述代码中添加：

rt = spu_pb2.ValueChunkProto()
rt.ParseFromString(xs[0].share_chunks[0])
print(int.from_bytes(rt.content, "little", signed=True))

rt = spu_pb2.ValueChunkProto()
rt.ParseFromString(xs[1].share_chunks[0])
print(int.from_bytes(rt.content, "little", signed=True))

执行后，得到结果：

4660903219305295116
-4660903219305295112

此时，x=4。另外，为了简单，我将share_max_chunk_size改为了8，这样share_chunks中只有一块数据。这是正确的吗？

[w-gc]

转成ValueChunkProto只是其中一小段，需要拼接起来的：

import spu.api as ppapi
import spu.spu_pb2 as spu_pb2
import numpy as np

config = spu_pb2.RuntimeConfig(
    protocol=spu_pb2.ProtocolKind.REF2K,
    field=spu_pb2.FieldType.FM64,
    fxp_fraction_bits=18,
    share_max_chunk_size=4,
)

wsize = 2
io = ppapi.Io(wsize, config)

x = np.random.randint(-100, 100, size=()); 
xs = io.make_shares(x, spu_pb2.Visibility.VIS_SECRET)

print(x)

for xss in xs:
    value = bytearray()
    for chk in xss.share_chunks:
        rt = spu_pb2.ValueChunkProto()
        rt.ParseFromString(chk)
        value += rt.content  # <---- follow ValueFromPyBindShare

    print(value)
    print(int.from_bytes(value, "little", signed=True))

[w-gc]

转成ValueChunkProto只是其中一小段，需要拼接起来的：

import spu.api as ppapi
import spu.spu_pb2 as spu_pb2
import numpy as np

config = spu_pb2.RuntimeConfig(
    protocol=spu_pb2.ProtocolKind.REF2K,
    field=spu_pb2.FieldType.FM64,
    fxp_fraction_bits=18,
    share_max_chunk_size=4,
)

wsize = 2
io = ppapi.Io(wsize, config)

x = np.random.randint(-100, 100, size=()); 
xs = io.make_shares(x, spu_pb2.Visibility.VIS_SECRET)

print(x)

for xss in xs:
    value = bytearray()
    for chk in xss.share_chunks:
        rt = spu_pb2.ValueChunkProto()
        rt.ParseFromString(chk)
        value += rt.content  # <---- follow ValueFromPyBindShare

    print(value)
    print(int.from_bytes(value, "little", signed=True))

这个做法是非常trick的，仅仅用于debug