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From: Keean Schupke <keean.schupke@googlemail.com>
Newsgroups: comp.lang.ada
Subject: Efficient Sequential Access to Arrays
Date: Sun, 15 Jul 2012 11:40:08 -0700 (PDT)
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Date: 2012-07-15T11:40:08-07:00
List-Id: <comp.lang.ada>

The Monte-Carlo simulator I am working on is now performing better in Ada t=
han in C++ using profile-guided compilation (57k simulations per second for=
 Ada 'vs' 56k simulations per second for C++).

However in order to achieve this performance I needed to rework the arrays =
as the use of Indexes was too slow. An example of this is lets say we are a=
ccessing element 5 from array A "A(5)" this requires a multiplication to ac=
cess (base_address + index * record_size). To access the neighbour A(6) als=
o requires a multiplication. Accessing the array sequentially requires a mu=
ltiplication per step.=20

Contrast this with C++ where we can return a pointer to the array element, =
and we just need to add the record_size to step to the next element.

So assuming we need this level of performance, what would be the best (and =
most idiomatic Ada) way to package this type of usage pattern as an abstrac=
t datatype?


Cheers,
Keean.