revert sqrt changes

Author: jbrockmendel

pandas/_libs/algos.pyx

@@ -27,10 +27,10 @@ from numpy cimport (ndarray,
 cdef double NaN = <double> np.NaN
 cdef double nan = NaN
 
-from libc.math cimport fabs
+from libc.math cimport fabs, sqrt
 
 # this is our util.pxd
-from util cimport numeric, get_nat, sqrt
+from util cimport numeric, get_nat
 
 import missing
 

pandas/_libs/lib.pyx

@@ -65,9 +65,9 @@ from missing cimport checknull
 
 cimport util
 cdef int64_t NPY_NAT = util.get_nat()
-from util cimport is_array, _checknull, sqrt
+from util cimport is_array, _checknull
 
-from libc.math cimport fabs
+from libc.math cimport fabs, sqrt
 
 
 def values_from_object(object o):

pandas/_libs/src/util.pxd

@@ -3,11 +3,6 @@ cimport numpy as cnp
 cimport cpython
 
 
-cdef extern from "headers/math.h":
-    # use this version instead of `from libc.math cimport sqrt`; see GH#18420
-    double sqrt(double x) nogil
-
-
 cdef extern from "numpy_helper.h":
     void set_array_not_contiguous(ndarray ao)
 

pandas/_libs/window.pyx

@@ -32,10 +32,11 @@ cdef double NaN = <double> np.NaN
 cdef inline int int_max(int a, int b): return a if a >= b else b
 cdef inline int int_min(int a, int b): return a if a <= b else b
 
-from util cimport numeric, sqrt
+from util cimport numeric
 
 cdef extern from "../src/headers/math.h":
     int signbit(double) nogil
+    double sqrt(double x) nogil
 
 
 # Cython implementations of rolling sum, mean, variance, skewness,