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b=rand(2) linalg.cg(a,b) (array([ nan, nan]), 1) linalg.cgs(a,b) (array([ nan, nan]), 1) linalg.solve(a,b) Traceback (most recent call last): File "<stdin>", line 1, in ? File "/usr/lib64/python2.4/site-packages/scipy/linalg/basic.py", line 103, in solve a1, b1 = map(asarray_chkfinite,(a,b)) File "/usr/lib64/python2.4/site-packages/numpy/lib/function_base.py", line 167, in asarray_chkfinite raise ValueError, "array must not contain infs or NaNs" ValueError: array must not contain infs or NaNs

Iterative solvers are inured to NaNs. Also

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linalg.hessenberg(a) array([[ nan, 1. ], [ 1. , 0. ]]) a array([[ nan, 1. ], [ 1. , 0. ]])

Nils