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Update documentation of random.uniform to reflect data type conversion behavior #3013

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Jun 4, 2021
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Update documentation of random.uniform to reflect data type conversion behavior #3013

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d31a5dc
Update documentation of random.uniform
jantonguirao Jun 2, 2021
d0c7051
Code review fixes
jantonguirao Jun 2, 2021
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6 changes: 5 additions & 1 deletion dali/operators/random/rng_base.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,10 @@ It should be added as parent to all RNG operators.)code")
.AddOptionalArg<std::vector<int>>("shape",
R"code(Shape of the output data.)code", nullptr, true)
.AddOptionalArg<DALIDataType>("dtype",
R"code(Output data type.)code", nullptr);
R"code(Output data type.

.. note::
The generated numbers are converted to the output data type, rounding and clamping if necessary.
)code", nullptr);

} // namespace dali
26 changes: 22 additions & 4 deletions dali/operators/random/uniform_distribution_cpu.cc
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Expand Up @@ -21,6 +21,10 @@ namespace dali {
DALI_SCHEMA(random__Uniform)
.DocStr(R"code(Generates random numbers following a uniform distribution.

It can be configured to produce a continuous uniform distribution in the ``range`` [min, max),
or a discrete uniform distribution where any of the specified ``values`` [v0, v1, ..., vn] occur
with equal probability.

The shape of the generated data can be either specified explicitly with a ``shape`` argument,
or chosen to match the shape of the input, if provided. If none are present, a scalar is
generated.
Expand All @@ -30,10 +34,15 @@ generated.
.AddOptionalArg("range",
R"code(Range ``[min, max)`` of a continuous uniform distribution.

This argument is mutually exclusive with ``values``.)code",
This argument is mutually exclusive with ``values``.

.. warning::
When specifying an integer type as ``dtype``, the generated numbers can go outside
the specified range, due to rounding.
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the generated numbers can go outside the specified range

Can't we clamp? It is a bit unexpected.

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@jantonguirao jantonguirao Jun 2, 2021 •
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So the RNG work like that, you generate the number in whatever is the natural type for the distribution, in this case float. Then if the user request the output data type to be a different type, we just ConvertSat(...). It's equivalent to doing fn.cast( fn.random.uniform(...), dtype=...), the numbers when converted to an integer data type, can go outside of the float range that was specified for the distribution. If the user needs a continuous distribution, it doesn't make much sense to request dtype to be an integer data type, I'd say.

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Make sense.

)code",
std::vector<float>{-1.0f, 1.0f}, true)
.AddOptionalArg<std::vector<float>>("values",
R"code(The discrete values produced by a discrete uniform distribution.
R"code(The discrete values [v0, v1, ..., vn] produced by a discrete uniform distribution.

This argument is mutually exclusive with ``range``.)code",
nullptr, true)
Expand All @@ -45,6 +54,10 @@ DALI_REGISTER_OPERATOR(random__Uniform, UniformDistribution<CPUBackend>, CPU);
DALI_SCHEMA(Uniform)
.DocStr(R"code(Generates random numbers following a uniform distribution.

It can be configured to produce a continuous uniform distribution in the ``range`` [min, max),
or a discrete uniform distribution where any of the specified ``values`` [v0, v1, ..., vn] occur
with equal probability.

The shape of the generated data can be either specified explicitly with a ``shape`` argument,
or chosen to match the shape of the input, if provided. If none are present, a scalar is
generated.
Expand All @@ -54,10 +67,15 @@ generated.
.AddOptionalArg("range",
R"code(Range ``[min, max)`` of a continuous uniform distribution.

This argument is mutually exclusive with ``values``.)code",
This argument is mutually exclusive with ``values``.

.. warning::
When specifying an integer type as ``dtype``, the generated numbers can go outside
the specified range, due to rounding.
)code",
std::vector<float>{-1.0f, 1.0f}, true)
.AddOptionalArg<std::vector<float>>("values",
R"code(The discrete values produced by a discrete uniform distribution.
R"code(The discrete values [v0, v1, ..., vn] produced by a discrete uniform distribution.

This argument is mutually exclusive with ``range``.)code",
nullptr, true)
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