Programming Forums > Application Development > Java

B3TA_SCR1PT3R · Dec 23rd, 2005, 10:51 PM

Hey i was wondering if there was a command for reducing the memory consumption, or CPU usage of a java program.
I dont know if this is typical of java programs, but im pushing around 20,000K just writing text to a file.
is this normal?, is it just my computer?, or something wrong in the code maybe?

heres some of the code: (its the only loop)

(Toggle Plain Text)

BufferedWriter bw = new BufferedWriter(new FileWriter(fileName));
Random rand = new Random();
for (int line = 0; line <= MAX; line++)
		{
			for (int num = 0; num <= MAX; num++)
			{
				intValue = rand.nextInt(90) + (10);
				bw.write(intValue + " ");
			}
			bw.newLine();
		}

andro · Dec 23rd, 2005, 11:19 PM

It's not pushing 20,000K because of you're writing to a text file. It's pushing 20,000K because of your nested for loops.

B3TA_SCR1PT3R · Dec 23rd, 2005, 11:38 PM

well i kinda need a nested for loop to make a square type output...is there anyway to reduce the memory consumption?

OpenLoop · Dec 23rd, 2005, 11:45 PM

I believe that this is normal because Java programs run on Java virtual machine instead of running natively on windows. Not sure though.

BTW, for loops don't fill up memory, they use up CPU power.

grumpy · Dec 24th, 2005, 1:28 AM

The memory usage isn't directly related to the nested loop (except for the fact that you're writing (MAX+1)*(MAX+1) integer values with separating whitespace to a file).

The memory usage is probably related to the fact that you're using a BufferedWriter. A BufferedWriter stores data (i.e. buffers it) in memory until it is flushed (i.e. physically written) to the file. That buffering can consume memory.

Writing directly to the FileWriter will probably eliminate the buffering (and hence the memory usage), but the trade-off will be I/O performance of your program. The disk (or other I/O device) is usually an I/O bottleneck for any program, and slowing that I/O down tends to have a very noticeable effect on how fast a file is written. A rough rule of thumb is that physically writing lots of little chunks to disk will be slower than writing a few big chunks. The whole purpose of buffered I/O is using memory to store data temporarily until bigger chunks are available to be written. The amount of memory consumed depends on how the buffering is implemented but most good-quality schemes will work within available memory resources. I'm not sure offhand how good the scheme used by BufferedWriter is.

Klipt · Dec 24th, 2005, 4:57 AM

I would assume 20 000k is well within 'available resources'

JavaMan · Dec 25th, 2005, 1:39 PM

I don't know if this would help, but you should close the reader after you are done using it.

Dec 23rd, 2005, 10:51 PM	#1
B3TA_SCR1PT3R Hobbyist Programmer Join Date: Jul 2005 Location: Dallas, Texas Posts: 101 Rep Power: 0	Reduce Memory Consumption Hey i was wondering if there was a command for reducing the memory consumption, or CPU usage of a java program. I dont know if this is typical of java programs, but im pushing around 20,000K just writing text to a file. is this normal?, is it just my computer?, or something wrong in the code maybe? heres some of the code: (its the only loop) (Toggle Plain Text) BufferedWriter bw = new BufferedWriter(new FileWriter(fileName)); Random rand = new Random(); for (int line = 0; line <= MAX; line++) { for (int num = 0; num <= MAX; num++) { intValue = rand.nextInt(90) + (10); bw.write(intValue + " "); } bw.newLine(); } BufferedWriter bw = new BufferedWriter(new FileWriter(fileName)); Random rand = new Random(); for (int line = 0; line <= MAX; line++) { for (int num = 0; num <= MAX; num++) { intValue = rand.nextInt(90) + (10); bw.write(intValue + " "); } bw.newLine(); } __________________ Hoes telling me to calm down but I'm like fuck that shit!

Dec 23rd, 2005, 11:38 PM	#3
B3TA_SCR1PT3R Hobbyist Programmer Join Date: Jul 2005 Location: Dallas, Texas Posts: 101 Rep Power: 0	well i kinda need a nested for loop to make a square type output...is there anyway to reduce the memory consumption? __________________ Hoes telling me to calm down but I'm like fuck that shit!

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Dec 23rd, 2005, 11:19 PM	#2
andro Professional Programmer Join Date: Oct 2005 Location: California Posts: 310 Rep Power: 3	It's not pushing 20,000K because of you're writing to a text file. It's pushing 20,000K because of your nested for loops.

Dec 23rd, 2005, 11:45 PM	#4
OpenLoop Expert Programmer Join Date: May 2005 Location: East Lansing, MI Posts: 663 Rep Power: 4	I believe that this is normal because Java programs run on Java virtual machine instead of running natively on windows. Not sure though. BTW, for loops don't fill up memory, they use up CPU power.

Dec 24th, 2005, 1:28 AM	#5
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,223 Rep Power: 5	The memory usage isn't directly related to the nested loop (except for the fact that you're writing (MAX+1)*(MAX+1) integer values with separating whitespace to a file). The memory usage is probably related to the fact that you're using a BufferedWriter. A BufferedWriter stores data (i.e. buffers it) in memory until it is flushed (i.e. physically written) to the file. That buffering can consume memory. Writing directly to the FileWriter will probably eliminate the buffering (and hence the memory usage), but the trade-off will be I/O performance of your program. The disk (or other I/O device) is usually an I/O bottleneck for any program, and slowing that I/O down tends to have a very noticeable effect on how fast a file is written. A rough rule of thumb is that physically writing lots of little chunks to disk will be slower than writing a few big chunks. The whole purpose of buffered I/O is using memory to store data temporarily until bigger chunks are available to be written. The amount of memory consumed depends on how the buffering is implemented but most good-quality schemes will work within available memory resources. I'm not sure offhand how good the scheme used by BufferedWriter is.

Dec 24th, 2005, 4:57 AM	#6
Klipt Hobbyist Programmer Join Date: Dec 2005 Posts: 118 Rep Power: 0	I would assume 20 000k is well within 'available resources'

Dec 25th, 2005, 1:39 PM	#7
JavaMan Newbie Join Date: Oct 2005 Posts: 29 Rep Power: 0	I don't know if this would help, but you should close the reader after you are done using it.

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Programming Forums > Application Development > Java

Reduce Memory Consumption