8000 DOC: expand reasoning behind npy_*floatstatus_barrer() by mattip · Pull Request #11073 · numpy/numpy · GitHub
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DOC: expand reasoning behind npy_*floatstatus_barrer() #11073

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Merged
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May 11, 2018
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DOC: expand reasoning behind npy_*floatstatus_barrer() #11073

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15 changes: 13 additions & 2 deletions doc/source/reference/c-api.coremath.rst
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Expand Up @@ -183,12 +183,19 @@ Those can be useful for precise floating point comparison.
* NPY_FPE_UNDERFLOW
* NPY_FPE_INVALID

Note that :c:func:`npy_get_floatstatus_barrier` is preferable as it prevents
agressive compiler optimizations reordering the call relative to
the code setting the status, which could lead to incorrect results.

.. versionadded:: 1.9.0

.. c:function:: int npy_get_floatstatus_barrier(char*)

Get floating point status. A pointer to a local variable is passed in to
prevent aggresive compiler optimizations from reodering this function call.
prevent aggresive compiler optimizations from reodering this function call
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typo

relative to the code setting the status, which could lead to incorrect
results.

Returns a bitmask with following possible flags:

* NPY_FPE_DIVIDEBYZERO
Expand All @@ -202,9 +209,13 @@ Those can be useful for precise floating point comparison.

Clears the floating point status. Returns the previous status mask.

Note that :c:func:`npy_clear_floatstatus_barrier` is preferable as it
prevents agressive compiler optimizations reordering the call relative to
the code setting the status, which could lead to incorrect results.

.. versionadded:: 1.9.0

.. c:function:: int npy_clear_floatstatus(char*)
.. c:function:: int npy_clear_floatstatus_barrier(char*)

Clears the floating point status. A pointer to a local variable is passed in to
prevent aggresive compiler optimizations from reodering this function call.
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5 changes: 4 additions & 1 deletion numpy/core/include/numpy/npy_math.h
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Expand Up @@ -528,10 +528,13 @@ int npy_clear_floatstatus_barrier(char*);
int npy_get_floatstatus_barrier(char*);
/*
* use caution with these - clang and gcc8.1 are known to reorder calls
* to this form of the function which can defeat the check
* to this form of the function which can defeat the check. The _barrier
* form of the call is preferable, where the argument is
* (char*)&local_variable
*/
int npy_clear_floatstatus(void);
int npy_get_floatstatus(void);

void npy_set_floatstatus_divbyzero(void);
void npy_set_floatstatus_overflow(void);
void npy_set_floatstatus_underflow(void);
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