Re: Array of a Class Type that contains an array where the sizes
of the array are not known at compile time.
On 1/14/2013 10:00 PM, GCRhoads@volcanomail.com wrote:
I care because it has a large effect on the efficiency of the
program. With contiguous memory locations, the program's memory
accesses will have a very high locality of reference resulting in a
much faster average memory access time due to the computer's memory
cache.
Are you also properly performing loop tiling to make sure that you
maximize cache reuse, testing and choosing optimal loop unrolling
parameters, and otherwise applying superoptimization techniques to your
code? If the answer to that question was either "no" or "I don't know
what you're saying," then I'll point out that the default
characteristics of Java's memory management is good enough performance
for you. If the answer was "yes", I will point out that you are almost
certainly using the wrong language.
I will also point out that doing |new int[5][10]| will almost certainly
be special-cased by the JVM into a dense multidimensional array (I
recall seeing some mention of multidimensional arrayOops when I was
poking about in OpenJDK to see if System.arraycopy might be using
copy-on-write).
--
Beware of bugs in the above code; I have only proved it correct, not
tried it. -- Donald E. Knuth