[petsc-users] Vec operations load/stores

[Justin Chang]

Hi everyone,

To somewhat follow up on a previous mail, I have a few questions regarding
the total bytes transferred for the following Vec operations (assuming Vec
size N and sequential mode):

VecTDot()
VecDot()
VecNorm()
VecScale()
VecSet()
VecAXPY()
VecAYPX()
VecWAXPY
VecPointwiseMult()

1) for the first three operations, I am loading two vectors so that's 2*N*8
bytes transferred. For storing, am I simply storing one scalar? Or am I
individually storing all N components as they are being summed up?

2) for the next five operations where I now have a scalar, am I loading it
only once or is it loaded N times?

3) Do any of the above operations "overlap" or depend on one another? For
instance if my solver invokes VecTDot X times does it also
invoke, say, VecPointwiseMult X times?

This is all theoretically speaking (i.e., assuming I am bypassing the cache
and write-allocate policy).

Thanks,
Justin
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