oldk1331 wrote:
>
> https://github.com/oldk1331/fricas/commit/1b4af9795519918465253e5628b3d33c75e92abd
>
> This is almost a rewrite of List, I make 4-space indentation
> and make code style consistent.
>
> Some notes:
> 1. QCAR/QCDR is actually slower than CAR/CDR. I compared them
> in SBCL using 'disassemble'.
I doubt if this comparison is relevant. Namely, QCAR/QCDR differ
from CAR/CDR by presence of declarations. sbcl documentation
clearly states that _at default safety setting_ declarations
are checked. This means that in default setting QCAR/QCDR
_alone_ is indeed slower. However:
- CAR/CDR gain speed due to weaker checking -- we can gain
more speed by skipping more checks, that is using 'safety 0'
At 'safety 0' sbcl blindly trusts declarations, so we get
more speed from QCAR/QCDR
- even with extra checks on average we gain: we pay cost of checks
in some places but then sbcl can infer types in other places
and _safely_ optimize object code
--
Waldek Hebisch
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