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Computation of the Tricomi confluent hypergeometric function can be ill-conditioned when it uses the sum of two 1F1 functions, as they can be nearly equal in size but opposite in sign. The mpmath function "hyperu" uses arbitrary precision internally and produces a result with 35 significant figures in default mode. How many of these digits are reliable? Does it depend on the parameters passed?

import mpmath

x = mpmath.hyperu(a, b + 1, u)
OneCricketeer
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I have just received an email from the main author of mpmath, Fredrik Johansson, confirming that the full 35 digits are usable. He writes "hyperu uses adaptive higher precision internally, so the result should nearly always be accurate to the full precision set by the user".

tcp
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