Measuring Run-Times with Java
TimeTheses
The following main method uses the static method "timethese" to find the runtime of several methods. The method "timethese" will time the runtime of all declared methods of the object that is the second argument, while the first argument is specifying how often each invocation is to be repeated.
TimeThese.javapublic class TimeThese
{ final static int size = 100;
public static void main( final java.lang.String[] _ )
{ timethese( 1000000, new java.lang.Object()
{ int dummy = 0; final java.util.List a;
{ a = new java.util.ArrayList( size );
for( int i = 0; i < size; ++i )
a.add( new java.lang.Integer( i )); }
void calc() { for( int i = 0; i < a.size(); ++i )
dummy +=(( java.lang.Integer )a.get( i )).intValue(); }
void len() { for (int i = 0, len = a.size(); i < len; i++ )
dummy +=(( java.lang.Integer )a.get( i )).intValue(); }
void down() { for (int i = a.size() - 1; i >= 0; i-- )
dummy +=(( java.lang.Integer )a.get( i )).intValue(); }}); }
public static void timethese
( final long count, final java.lang.Object o )
{ try{ java.lang.Class c = o.getClass();
java.lang.reflect.Method m[] = c.getDeclaredMethods();
for( int i = 0; i < m.length; ++i )
{ java.lang.reflect.Method m0 = m[ i ];
java.lang.System.out.println( m0.getName() );
long a = java.lang.System.nanoTime();
for( long j = count; j-- > 0; )m0.invoke( o, null );
long b = java.lang.System.nanoTime();
java.lang.System.out.println( b - a ); }}
catch( final java.lang.Throwable t )
{ java.lang.System.err.println( t ); }}}System.outlen
562045124
calc
390348480
down
300342781
TimeThese1
The following is a somewhat more elaborated version. I have not yet found the time to comment the details.
It sorts the results and formats the output more nicely.
And it has an outer loop around everything so that all methods are treated more equal with regard to HotSpot optimization.
TimeThese1.javaclass TimeThings
{ final java.lang.String newLine;
public TimeThings( final java.lang.String newLine )
{ this.newLine = newLine; }
public java.lang.String timethese
( final long count, final java.lang.Object o )
{ java.lang.String report = "";
final java.util.Map<java.lang.String,java.lang.Long> sum =
new java.util.HashMap<java.lang.String,java.lang.Long>();
try{ final java.lang.Class c = o.getClass();
final java.lang.reflect.Method m[] = c.getDeclaredMethods();
final int mLength = m.length;
for( int i = 0; i < mLength; ++i )
{ sum.put( m[ i ].getName(), 0L ); }
for( int r = 0; r < 100; ++r )
{ for( int i = 0; i < mLength; ++i )
{ final java.lang.reflect.Method m_ = m[ i ];
final java.lang.String mName = m_.getName();
final long a = System.nanoTime();
for( long j = count; j-- > 0; )m_.invoke( o, null );
final long dt = System.nanoTime() - a;
sum.put( mName, sum.get( mName )+ dt ); }}
final java.util.TreeMap<Long,java.lang.String> sorted =
new java.util.TreeMap<Long,java.lang.String>();
int mxLen = -1; for( int i = 0; i < mLength; ++i )
{ sorted.put( new Long( sum.get( m[ i ].getName() ), i ), m[ i ].getName() );
final int len = m[ i ].getName().length() +
java.lang.String.format( "%d", sum.get( m[ i ].getName() )).length();
if( len > mxLen )mxLen = len; }
for( Long l : sorted.keySet() )
{ final java.lang.String name = sorted.get( l );
final int len =( name + java.lang.String.format( "%d", l.longValue() ) ).length();
report += name +
java.lang.String.format("%" +( mxLen - len + 1 )+ "s", "" ) +
java.lang.String.format( "%d", l.longValue() ) + newLine; }}
catch( final Throwable t ){ System.err.println( t ); } return report; }}
public class TimeThese1
{ public static void main( final java.lang.String[] _ )
{ TimeThings timeThings = new TimeThings( java.lang.String.format( "%n" ));
java.lang.System.out.println
( timeThings.timethese( 1000, new Object()
{ final int size = 10000;
java.util.List a; { a = new java.util.ArrayList( size );
for(int i = 0; i < size; ++i )a.add( new java.lang.Integer( i )); }
void nop(){}
int nop1(){ return (( java.lang.Integer )a.get( 0 )).intValue(); }
int calc(){ int s = 0; for( int i = 0; i < a.size(); ++i )
s += (( java.lang.Integer )a.get( i )).intValue(); return s; }
int len(){ int s = 0; final int aSize = a.size();
for( int i = 0 ; i < aSize; ++i )
s += (( java.lang.Integer )a.get( i )).intValue(); return s; }
int down(){ int s = 0; for( int i = a.size(); --i >= 0; )
s += (( java.lang.Integer )a.get( i )).intValue(); return s; }
int unroll()
{ int sa = 0, sb = 0, sc = 0, sd = 0, se = 0, i = a.size() - 1;
for( ;i >= 4; i -= 5 )
{ sa +=(( java.lang.Integer )a.get( i )).intValue();
sb +=(( java.lang.Integer )a.get( i - 1 )).intValue();
sc +=(( java.lang.Integer )a.get( i - 2 )).intValue();
sd +=(( java.lang.Integer )a.get( i - 3 )).intValue();
se +=(( java.lang.Integer )a.get( i - 4 )).intValue(); }
for( ; i >= 0; --i )sa +=(( java.lang.Integer )a.get( i )).intValue();
int s = sa + sb + sc + sd + se; return s; }})); }}
class Long implements java.lang.Comparable<Long>
{ final java.lang.Long me; final java.lang.Integer bias;
public Long( final java.lang.Long me, final int bias )
{ this.me = me; this.bias = new java.lang.Integer( bias ); }
public int compareTo( final Long other )
{ final int product = this.me.compareTo( other.me );
final int product1 =
product == 0 ? -this.bias.compareTo( other.bias ) : product;
return product1; }
public long longValue(){ return this.me.longValue(); }}System.outnop1 54363127
nop 91908176
down 239960440
calc 264872022
len 306160015
unroll 398913832