46 lines
1.8 KiB
Plaintext
46 lines
1.8 KiB
Plaintext
Copyright (c) 2002, 2018, Oracle and/or its affiliates. All rights reserved.
|
|
DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
|
|
|
|
This code is free software; you can redistribute it and/or modify it
|
|
under the terms of the GNU General Public License version 2 only, as
|
|
published by the Free Software Foundation.
|
|
|
|
This code is distributed in the hope that it will be useful, but WITHOUT
|
|
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
|
|
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
|
|
version 2 for more details (a copy is included in the LICENSE file that
|
|
accompanied this code).
|
|
|
|
You should have received a copy of the GNU General Public License version
|
|
2 along with this work; if not, write to the Free Software Foundation,
|
|
Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
|
|
|
|
Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
|
|
or visit www.oracle.com if you need additional information or have any
|
|
questions.
|
|
|
|
Strength Reduction
|
|
------------------
|
|
|
|
Strength reduction replaces an expansive operation by a cheaper one, such as
|
|
multiplication by addition or subtraction, multiplication instead of
|
|
exponentiation; use compound assignment operators such as += wherever possible,
|
|
changing code of the form a[i] = a[i] + x to a[i] += x, since they result in
|
|
fewer bytecode instructions; use shifts instead of multiplication by powers of
|
|
two, etc.
|
|
|
|
For example:
|
|
|
|
x ** 2 = x * x
|
|
2.0 * x = x + x
|
|
x / 2 = x * 0.5
|
|
|
|
|
|
Induction Variable
|
|
------------------
|
|
|
|
A variable is called an induction variables of a loop if every time the variable
|
|
changes values it is incremented or decrmented by some constant.
|
|
Basic induction variables i whose only assignments within the loop is of the
|
|
form i += c, where c is a constant.
|