Greetings:

Got a nasty surprise today.  have a non-trivial J app with the following
supporting original definitions:

sum =. +/
dot =. +/ . *
sqrd =. *:
ssq =. +/ @: sqrd


Which I changed (thinking I was being elegant) to

sum =. +/
dot =. sum . *
sqrd =. *:
ssq =. sum @: sqrd

After this change the run time increased by a factor of 5!

Insights?
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