ENH: Convert finfo.tiny to finfo.smallest_normal (#76292)

Fixes #70909, by a straightforward search and replace discussed in #70909.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/76292
Approved by: https://github.com/mruberry

docs/source/type_info.rst

@@ -19,22 +19,23 @@ A :class:`torch.finfo` is an object that represents the numerical properties of
 
 A :class:`torch.finfo` provides the following attributes:
 
-==========  =====   ========================================
-Name        Type    Description
-==========  =====   ========================================
-bits        int     The number of bits occupied by the type.
-eps         float   The smallest representable number such that ``1.0 + eps != 1.0``.
-max         float   The largest representable number.
-min         float   The smallest representable number (typically ``-max``).
-tiny        float   The smallest positive normal number. See notes.
-resolution  float   The approximate decimal resolution of this type, i.e., ``10**-precision``.
-==========  =====   ========================================
+===============        =====   ==========================================================================
+Name                   Type    Description
+===============        =====   ==========================================================================
+bits                   int     The number of bits occupied by the type.
+eps                    float   The smallest representable number such that ``1.0 + eps != 1.0``.
+max                    float   The largest representable number.
+min                    float   The smallest representable number (typically ``-max``).
+tiny                   float   The smallest positive normal number. Equivalent to ``smallest_normal``.
+smallest_normal        float   The smallest positive normal number. See notes.
+resolution             float   The approximate decimal resolution of this type, i.e., ``10**-precision``.
+===============        =====   ==========================================================================
 
 .. note::
   The constructor of :class:`torch.finfo` can be called without argument, in which case the class is created for the pytorch default dtype (as returned by :func:`torch.get_default_dtype`).
 
 .. note::
-  `tiny` returns the smallest *normal* number, but there are smaller
+  `smallest_normal` returns the smallest *normal* number, but there are smaller
   subnormal numbers. See https://en.wikipedia.org/wiki/Denormal_number
   for more information.
 

test/test_type_info.py

@@ -63,6 +63,7 @@ class TestDTypeInfo(TestCase):
         self.assertEqual(xinfo.min, -3.38953e+38)
         self.assertEqual(xinfo.eps, 0.0078125)
         self.assertEqual(xinfo.tiny, 1.17549e-38)
+        self.assertEqual(xinfo.tiny, xinfo.smallest_normal)
         self.assertEqual(xinfo.resolution, 0.01)
         self.assertEqual(xinfo.dtype, "bfloat16")
         torch.set_default_dtype(x.dtype)

torch/_C/__init__.pyi.in

@@ -87,6 +87,7 @@ class finfo:
     max: _float
     eps: _float
     tiny: _float
+    smallest_normal: _float
     resolution: _float
     dtype: str
 

torch/csrc/TypeInfo.cpp

@@ -168,13 +168,18 @@ static PyObject* THPIInfo_dtype(THPIInfo* self, void*) {
   });
 }
 
-static PyObject* THPFInfo_tiny(THPFInfo* self, void*) {
+static PyObject* THPFInfo_smallest_normal(THPFInfo* self, void*) {
   return AT_DISPATCH_FLOATING_AND_COMPLEX_TYPES_AND2(at::kHalf, at::ScalarType::BFloat16, self->type, "min", [] {
     return PyFloat_FromDouble(
         std::numeric_limits<at::scalar_value_type<scalar_t>::type>::min());
   });
 }
 
+static PyObject* THPFInfo_tiny(THPFInfo* self, void*) {
+  // see gh-70909, essentially the array_api prefers smallest_normal over tiny
+  return THPFInfo_smallest_normal(self, nullptr);
+}
+
 static PyObject* THPFInfo_resolution(THPFInfo* self, void*) {
   return AT_DISPATCH_FLOATING_AND_COMPLEX_TYPES_AND2(at::kHalf, at::ScalarType::BFloat16, self->type, "digits10", [] {
     return PyFloat_FromDouble(
@@ -197,6 +202,7 @@ PyObject* THPFInfo_str(THPFInfo* self) {
   oss << ", min=" << PyFloat_AsDouble(THPFInfo_min(self, nullptr));
   oss << ", max=" << PyFloat_AsDouble(THPFInfo_max(self, nullptr));
   oss << ", eps=" << PyFloat_AsDouble(THPFInfo_eps(self, nullptr));
+  oss << ", smallest_normal=" << PyFloat_AsDouble(THPFInfo_smallest_normal(self, nullptr));
   oss << ", tiny=" << PyFloat_AsDouble(THPFInfo_tiny(self, nullptr));
   oss << ", dtype=" << PyUnicode_AsUTF8(THPFInfo_dtype(self, nullptr)) << ")";
 
@@ -222,6 +228,7 @@ static struct PyGetSetDef THPFInfo_properties[] = {
     {"eps", (getter)THPFInfo_eps, nullptr, nullptr, nullptr},
     {"max", (getter)THPFInfo_max, nullptr, nullptr, nullptr},
     {"min", (getter)THPFInfo_min, nullptr, nullptr, nullptr},
+    {"smallest_normal", (getter)THPFInfo_smallest_normal, nullptr, nullptr, nullptr},
     {"tiny", (getter)THPFInfo_tiny, nullptr, nullptr, nullptr},
     {"resolution", (getter)THPFInfo_resolution, nullptr, nullptr, nullptr},
     {"dtype", (getter)THPFInfo_dtype, nullptr, nullptr, nullptr},