[Numpy-tickets] [NumPy] #1008: Loss of precision in (complex) arcsinh & arctanh

NumPy numpy-tickets@scipy....
Sun Feb 15 06:16:20 CST 2009


#1008: Loss of precision in (complex) arcsinh & arctanh
------------------------+---------------------------------------------------
 Reporter:  pv          |       Owner:  somebody                 
     Type:  defect      |      Status:  new                      
 Priority:  normal      |   Milestone:  1.3.0                    
Component:  numpy.core  |     Version:  devel                    
 Severity:  minor       |    Keywords:  precision arcsinh arctanh
------------------------+---------------------------------------------------
 Numpy's complex `arcsinh` and `arctanh` suffer from loss of precision at
 small arguments:
 {{{
 >>> import numpy as np
 >>> np.__version__
 '1.3.0.dev6366'
 >>> np.arcsinh(1e-50)
 1e-50
 >>> np.arcsinh(1e-50+0j)
 0j
 >>> np.arctanh(1e-50)
 1e-50
 >>> np.arctanh(1e-50+0j)
 0j
 }}}
 However, complex `arcsin` and `arctan` are OK:
 {{{
 >>> np.arcsin(1e-50 + 0j)
 (1e-50-0j)
 >>> np.arctan(1e-50 + 0j)
 (1e-50+0j)
 }}}

-- 
Ticket URL: <http://scipy.org/scipy/numpy/ticket/1008>
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