Re: Logical handling
Dieter Britz wrote:
I want to handle matrices of type logical, and I reckon that
these ought to be done faster than the equivalent integer
matrices with MOD(*,2) hung on. However, on my Intel compiler,
the two came out almost exactly the same in cpu time. Clearly,
logicals are stored in whole words, rather than bits.
Is this general for compilers, or is it an Intel thing?
--
It's general on virtually any existing processor. For Fortran LOGICAL
is, as you note, equivalent in length to INTEGER and does not have an
intrinsic bit type. Since Intel processors in particular (and
virtually all in general) are word- or byte-addressable, the faster
operation(s) are on words, and addressing individual bits would, if
implemented, be more compute-intensive than the equivalent word
operation(s).
As for the difference between direct use of LOGICAL and INTEGER w/
MOD() not showing significant difference, that is probably owing to the
optimization by the compiler and the size/structure of the test(s).
.
Relevant Pages
- Re: Logical handling
... logicals are stored in whole words, ... or is it an Intel thing? ... MODnot showing significant difference, that is probably owing to the ... optimization by the compiler and the size/structure of the test. ...
(comp.lang.fortran) - Re: Logical handling
... logicals are stored in whole words, ... or is it an Intel thing? ... a logical spanning a byte involves the same memory bandwidth as ... optimization by the compiler and the size/structure of the test. ...
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(comp.lang.fortran) |
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