Page Menu
Home
c4science
Search
Configure Global Search
Log In
Files
F79348419
ExponentialGenerator.java
No One
Temporary
Actions
Download File
Edit File
Delete File
View Transforms
Subscribe
Mute Notifications
Award Token
Subscribers
None
File Metadata
Details
File Info
Storage
Attached
Created
Sun, Aug 25, 23:13
Size
4 KB
Mime Type
text/x-c
Expires
Tue, Aug 27, 23:13 (2 d)
Engine
blob
Format
Raw Data
Handle
20176539
Attached To
R7507 YCSB
ExponentialGenerator.java
View Options
/**
* Copyright (c) 2011 Yahoo! Inc. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you
* may not use this file except in compliance with the License. You
* may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
* implied. See the License for the specific language governing
* permissions and limitations under the License. See accompanying
* LICENSE file.
*/
package
com.yahoo.ycsb.generator
;
import
com.yahoo.ycsb.Utils
;
/**
* A generator of an exponential distribution. It produces a sequence
* of time intervals according to an exponential
* distribution. Smaller intervals are more frequent than larger
* ones, and there is no bound on the length of an interval. When you
* construct an instance of this class, you specify a parameter gamma,
* which corresponds to the rate at which events occur.
* Alternatively, 1/gamma is the average length of an interval.
*/
public
class
ExponentialGenerator
extends
NumberGenerator
{
// What percentage of the readings should be within the most recent exponential.frac portion of the dataset?
public
static
final
String
EXPONENTIAL_PERCENTILE_PROPERTY
=
"exponential.percentile"
;
public
static
final
String
EXPONENTIAL_PERCENTILE_DEFAULT
=
"95"
;
// What fraction of the dataset should be accessed exponential.percentile of the time?
public
static
final
String
EXPONENTIAL_FRAC_PROPERTY
=
"exponential.frac"
;
public
static
final
String
EXPONENTIAL_FRAC_DEFAULT
=
"0.8571428571"
;
// 1/7
/**
* The exponential constant to use.
*/
private
double
_gamma
;
/******************************* Constructors **************************************/
/**
* Create an exponential generator with a mean arrival rate of
* gamma. (And half life of 1/gamma).
*/
public
ExponentialGenerator
(
double
mean
)
{
_gamma
=
1.0
/
mean
;
}
public
ExponentialGenerator
(
double
percentile
,
double
range
)
{
_gamma
=
-
Math
.
log
(
1.0
-
percentile
/
100.0
)
/
range
;
//1.0/mean;
}
/****************************************************************************************/
/**
* Generate the next item as a long. This distribution will be skewed toward lower values; e.g. 0 will
* be the most popular, 1 the next most popular, etc.
* @return The next item in the sequence.
*/
@Override
public
Double
nextValue
()
{
return
-
Math
.
log
(
Utils
.
random
().
nextDouble
())
/
_gamma
;
}
@Override
public
double
mean
()
{
return
1.0
/
_gamma
;
}
public
static
void
main
(
String
args
[])
{
ExponentialGenerator
e
=
new
ExponentialGenerator
(
90
,
100
);
int
j
=
0
;
for
(
int
i
=
0
;
i
<
1000
;
i
++)
{
if
(
e
.
nextValue
()
<
100
)
{
j
++;
}
}
System
.
out
.
println
(
"Got "
+
j
+
" hits. Expect 900"
);
}
}
Event Timeline
Log In to Comment