proto type for many to one type serialization

[antonydellavecchia]

This pull request should not neccesarily be merged.

It is just to demonstrate a possible mechanic for having a many types to one serialization
where multiple types share the same encoding.

I put it in a pull request to highlight the changes and to start to discuss if this is viable solution and
to discuss the potential pitfalls of such a mechanism.

I have an unsafe line of code that I comment on, but this should be fixable, I just couldn't figure out
why sometimes string(fpField) = "Nemo.fpField" and sometimes it is string(fpField) = "fpField"

[antonydellavecchia]

Default type storing FqField only the type name has changed.

{
  "_ns": {
    "Oscar": [
      "https://github.com/oscar-system/Oscar.jl",
      "1.3.0-DEV-2ebe51fbb819d32ee59f8f43cd3fb506b796b249"
    ]
  },
  "_type": "FiniteField",
  "data": "2",
  "id": "aad30397-63b7-4082-a55f-4cc425217b83"
}

Non default types have _instance keyword which is a string of the Oscar type that it was before serialization.

{
  "_instance": "fpField",
  "_ns": {
    "Oscar": [
      "https://github.com/oscar-system/Oscar.jl",
      "1.3.0-DEV-2ebe51fbb819d32ee59f8f43cd3fb506b796b249"
    ]
  },
  "_type": "FiniteField",
  "data": "2"
}

[micjoswig]

Should I be irritated by these comments in the code?

if haskey(s.obj, :_instance)
   # to be safe we need this check but I can't figure out how to get sending
   # types to strings to behave properly
   #s.obj["_instance"] in keys(reverse_type_map[s.obj[type_key]])
   T = eval(Meta.parse(s.obj["_instance"]))
 else
   T = decode_type(s)
 end

What does it mean that "I can't figure out how to get sending types to strings to behave properly"?

[micjoswig]

See above.

[antonydellavecchia]

Should I be irritated by these comments in the code?

if haskey(s.obj, :_instance)
   # to be safe we need this check but I can't figure out how to get sending
   # types to strings to behave properly
   #s.obj["_instance"] in keys(reverse_type_map[s.obj[type_key]])
   T = eval(Meta.parse(s.obj["_instance"]))
 else
   T = decode_type(s)
 end

What does it mean that "I can't figure out how to get sending types to strings to behave properly"?

This is mainly a todo for me, I describe this issue in the description for the pull request. It appears that string(fpField) = "Nemo.fpField" and sometimes it is string(fpField) = "fpField". I do believe this is fixable, I just haven't had the time to figure out how yet.

I've commented in the code the places where the unexpected results are happening (see following commit)

[antonydellavecchia]

The changes would have the following consequences on the example in the paper.
With a bit of work it should also be possible to not have the "_instance" key appear in the types such as PolyRing

{
  "_ns": {
    "Oscar": [
      "https://github.com/oscar-system/Oscar.jl",
      "1.3.0-DEV-4d1a3ffa24b8e340470afa6b40c02150e3558b4e"
    ]
  },
  "_refs": {
    "0377c284-0b31-4d83-b009-0776e883e80b": {
      "_instance": "FqMPolyRing",
      "_type": "MPolyRing",
      "data": {
        "base_ring": "8c4b9843-a0e1-4306-aff3-1a8dca4954a0",
        "symbols": [
          "y",
          "z"
        ]
      }
    },
    "8c4b9843-a0e1-4306-aff3-1a8dca4954a0": {
      "_type": "FiniteField",
      "data": {
        "def_pol": {
          "_type": {
            "name": "PolyRingElem",
            "params": "c22521f2-ddaf-4125-9c34-c5294f59602d"
          },
          "data": [
            [
              "0",
              "3"
            ],
            [
              "1",
              "6"
            ],
            [
              "2",
              "1"
            ]
          ]
        }
      }
    },
    "c22521f2-ddaf-4125-9c34-c5294f59602d": {
      "_instance": "FqPolyRing",
      "_type": "PolyRing",
      "data": {
        "base_ring": "fd0fa33d-250c-46e6-8d11-0ff6969625bd",
        "symbols": [
          "x"
        ]
      }
    },
    "fd0fa33d-250c-46e6-8d11-0ff6969625bd": {
      "_type": "FiniteField",
      "data": "7"
    }
  },
  "_type": {
    "name": "MPolyRingElem",
    "params": "0377c284-0b31-4d83-b009-0776e883e80b"
  },
  "data": [
    [
      [
        "3",
        "4"
      ],
      [
        [
          "0",
          "2"
        ]
      ]
    ],
    [
      [
        "1",
        "0"
      ],
      [
        [
          "1",
          "5"
        ]
      ]
    ],
    [
      [
        "0",
        "2"
      ],
      [
        [
          "0",
          "3"
        ],
        [
          "1",
          "1"
        ]
      ]
    ],
    [
      [
        "0",
        "0"
      ],
      [
        [
          "0",
          "1"
        ]
      ]
    ]
  ]
}

[antonydellavecchia]

with the latest commit example file looks like this

{
  "_ns": {
    "Oscar": [
      "https://github.com/oscar-system/Oscar.jl",
      "1.3.0-DEV-4d1a3ffa24b8e340470afa6b40c02150e3558b4e"
    ]
  },
  "_refs": {
    "2f5028cc-0fd6-4381-8f7e-0ff1520da04d": {
      "_instance": "FqPolyRing",
      "_type": "PolyRing",
      "data": {
        "base_ring": "d58dcad8-17fa-48aa-aaf9-3a3cd3f86fd4",
        "symbols": [
          "x"
        ]
      }
    },
    "5c637058-63cd-4773-84f1-965164c98ab5": {
      "_instance": "FqField",
      "_type": "FiniteField",
      "data": {
        "def_pol": {
          "_type": {
            "name": "PolyRingElem",
            "params": "2f5028cc-0fd6-4381-8f7e-0ff1520da04d"
          },
          "data": [
            [
              "0",
              "3"
            ],
            [
              "1",
              "6"
            ],
            [
              "2",
              "1"
            ]
          ]
        }
      }
    },
    "d58dcad8-17fa-48aa-aaf9-3a3cd3f86fd4": {
      "_instance": "FqField",
      "_type": "FiniteField",
      "data": "7"
    },
    "dc9554a8-0ed5-4504-9c21-7760d6c4d02c": {
      "_instance": "FqMPolyRing",
      "_type": "MPolyRing",
      "data": {
        "base_ring": "5c637058-63cd-4773-84f1-965164c98ab5",
        "symbols": [
          "y",
          "z"
        ]
      }
    }
  },
  "_type": {
    "name": "MPolyRingElem",
    "params": "dc9554a8-0ed5-4504-9c21-7760d6c4d02c"
  },
  "data": [
    [
      [
        "3",
        "4"
      ],
      [
        [
          "0",
          "2"
        ]
      ]
    ],
    [
      [
        "1",
        "0"
      ],
      [
        [
          "1",
          "5"
        ]
      ]
    ],
    [
      [
        "0",
        "2"
      ],
      [
        [
          "0",
          "3"
        ],
        [
          "1",
          "1"
        ]
      ]
    ],
    [
      [
        "0",
        "0"
      ],
      [
        [
          "0",
          "1"
        ]
      ]
    ]
  ]
}

[micjoswig]

We agreed that there should be an _instance entry every time where the many to one map is not bijective, even if suitable OSCAR defaults are in place.

With this addition the PR is good for merge IMHO.