Heisenbug bug

As stated in Wikipedia,

In computer programming jargon, a heisenbug is a software bug that seems to disappear or alter its behavior when one attempts to study it .

I recently came across one whilst developing a small program:

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NaN debugging

I recently came accross a bug in a software I am contributing to causing some NaN to appear. In this software, I want to solve a system Ax=b using a sparse linear solver( Hypre ) but it failed to converge showing this message:

ERROR detected by Hypre ...  BEGIN
ERROR -- hypre_PCGSolve: INFs and/or NaNs detected in input.
User probably placed non-numerics in supplied b.
Returning error flag += 101.  Program not terminated.
ERROR detected by Hypre ...  END
Hypre PCG finish in 0 iterations with a final res norm of 0

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terminal shortcuts

Here is some command line shortcuts that can be usefull:

• !! grabs the last command you entered and substitutes it into the current text.
• ctrl + a beginning of a line
• ctrl + e end of a line
• ctrl + b back from a character
• ctrl + f forward from a character
• ESC + b back from a word
• ESC + f forward from a word

I founds these information here

ARCHIVE 2013 floating point arithmetic and precision

In this post, I want to talk a bit about floating-point arithmetic and precision applied to GPUs!

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