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Diffstat (limited to 'doc/source/reference/random/new-or-different.rst')
| -rw-r--r-- | doc/source/reference/random/new-or-different.rst | 56 |
1 files changed, 28 insertions, 28 deletions
diff --git a/doc/source/reference/random/new-or-different.rst b/doc/source/reference/random/new-or-different.rst index 8f4a70540..9b5bf38e5 100644 --- a/doc/source/reference/random/new-or-different.rst +++ b/doc/source/reference/random/new-or-different.rst @@ -5,17 +5,9 @@ What's New or Different ----------------------- -.. warning:: - - The Box-Muller method used to produce NumPy's normals is no longer available - in `Generator`. It is not possible to reproduce the exact random - values using ``Generator`` for the normal distribution or any other - distribution that relies on the normal such as the `Generator.gamma` or - `Generator.standard_t`. If you require bitwise backward compatible - streams, use `RandomState`, i.e., `RandomState.gamma` or - `RandomState.standard_t`. - -Quick comparison of legacy :ref:`mtrand <legacy>` to the new `Generator` +NumPy 1.17.0 introduced `Generator` as an improved replacement for +the :ref:`legacy <legacy>` `RandomState`. Here is a quick comparison of the two +implementations. ================== ==================== ============= Feature Older Equivalent Notes @@ -44,21 +36,17 @@ Feature Older Equivalent Notes ``high`` interval endpoint ================== ==================== ============= -And in more detail: - -* Simulate from the complex normal distribution - (`~.Generator.complex_normal`) * The normal, exponential and gamma generators use 256-step Ziggurat methods which are 2-10 times faster than NumPy's default implementation in `~.Generator.standard_normal`, `~.Generator.standard_exponential` or - `~.Generator.standard_gamma`. - + `~.Generator.standard_gamma`. Because of the change in algorithms, it is not + possible to reproduce the exact random values using ``Generator`` for these + distributions or any distribution method that relies on them. .. ipython:: python - from numpy.random import Generator, PCG64 import numpy.random - rng = Generator(PCG64()) + rng = np.random.default_rng() %timeit -n 1 rng.standard_normal(100000) %timeit -n 1 numpy.random.standard_normal(100000) @@ -74,18 +62,25 @@ And in more detail: * `~.Generator.integers` is now the canonical way to generate integer - random numbers from a discrete uniform distribution. The ``rand`` and - ``randn`` methods are only available through the legacy `~.RandomState`. - This replaces both ``randint`` and the deprecated ``random_integers``. -* The Box-Muller method used to produce NumPy's normals is no longer available. + random numbers from a discrete uniform distribution. This replaces both + ``randint`` and the deprecated ``random_integers``. +* The ``rand`` and ``randn`` methods are only available through the legacy + `~.RandomState`. +* `Generator.random` is now the canonical way to generate floating-point + random numbers, which replaces `RandomState.random_sample`, + `sample`, and `ranf`, all of which were aliases. This is consistent with + Python's `random.random`. * All bit generators can produce doubles, uint64s and uint32s via CTypes (`~PCG64.ctypes`) and CFFI (`~PCG64.cffi`). This allows these bit generators to be used in numba. * The bit generators can be used in downstream projects via Cython. +* All bit generators use `SeedSequence` to :ref:`convert seed integers to + initialized states <seeding_and_entropy>`. * Optional ``dtype`` argument that accepts ``np.float32`` or ``np.float64`` to produce either single or double precision uniform random variables for - select distributions + select distributions. `~.Generator.integers` accepts a ``dtype`` argument + with any signed or unsigned integer dtype. * Uniforms (`~.Generator.random` and `~.Generator.integers`) * Normals (`~.Generator.standard_normal`) @@ -94,9 +89,10 @@ And in more detail: .. ipython:: python - rng = Generator(PCG64(0)) - rng.random(3, dtype='d') - rng.random(3, dtype='f') + rng = np.random.default_rng() + rng.random(3, dtype=np.float64) + rng.random(3, dtype=np.float32) + rng.integers(0, 256, size=3, dtype=np.uint8) * Optional ``out`` argument that allows existing arrays to be filled for select distributions @@ -111,6 +107,7 @@ And in more detail: .. ipython:: python + rng = np.random.default_rng() existing = np.zeros(4) rng.random(out=existing[:2]) print(existing) @@ -121,9 +118,12 @@ And in more detail: .. ipython:: python - rng = Generator(PCG64(123456789)) + rng = np.random.default_rng() a = np.arange(12).reshape((3, 4)) a rng.choice(a, axis=1, size=5) rng.shuffle(a, axis=1) # Shuffle in-place a + +* Added a method to sample from the complex normal distribution + (`~.Generator.complex_normal`) |