Improving computer perfomance

Moore’s Law
Number of transistors on a microchip doubles every 18 months.
Predictions based on Moore’s Law
Processing power (speed) doubles every 18 months.
Storage capacity of RAM and hard disk increases exponentially.
Computer price is decreasing

Bottlenecks

Bottlenecks

Bottlenecks (critical element)
Bottleneck is a step within a series of steps that takes the longest time to complete.
Time required to perform a task consisting of several steps may be delayed by the bottleneck step.

Bottlenecks (continued)
Typical bottlenecks:
Cache
RAM
I/O (Information transfer, bus, hard drive)
Video card (particularly for 3-D gaming)

Bottlenecks (continued)
To speed up performance of a system:
Use profiling tools to measure each section’s time taken to complete to determine the bottleneck steps
Improve upon the bottleneck steps
VTune
CodeAnalyst
AQtime

Vtune Performance Analyzer

Throughput and Latency
Throughput (пропускная способность) - the rate at which data flows through the system
For example, a computer might execute 500 million instructions per second

Throughput and Latency
Latency (access time) - time required to complete an individual operation
For example, it might take five seconds to launch an application, or two minutes to reboot the entire system.

Latency
Image is a 1 MB file
Throughput 10 megabits per second
Latency to display the image will be at least 0.8 seconds.

Throughput and Latency

Your turn
If you are selecting a provider for your Web server's network connection, you will be more concerned with ….?
A) Throughput
B) Latency

Your turn
If you are a user of the same web server, you will certainly be concerned with…. ?
A) Throughput
B) Latency

Data Compression
Storing data in a format that requires less space than usual
When data is compressed, the file size shrinks.
Amount of shrinkage is referred as compression ratio

Data Compression
Codec (Compressor and Decompressor) - hardware or software used to compress and decompress

Disk Compression
Shrinks the files and places it in a special volume on the hard disk.
Disk volume is a disk or an area of a disk which has a unique name and is treated as a hard disk.
Use storage space more efficiently

Disk Compression

Disk Compression (continued)
Advantages :
Gain storage space without any additional hardware.
Under optimal circumstances, the hard disk capacity is doubled.
Disadvantages:
File error in the compressed volume means the loss of all the data in that volume

File Compression
Shrinks one or more into single smaller file.
Compressed file cannot be used until it is uncompressed.
WinZIP and WinRAR
Compressing a file is called Zipping
Uncompressing a file is known as Unzipping

Text File Compression
Adaptive Pattern Substitution:
Designed for compressing text files.
Scans the entire text,
Looks for patterns of two or more bytes,
Substitutes a byte pattern and make a dictionary entry for it.
Effectiveness depends on the content of the document

Text File Compression
Another type of compression scans and finds repeated words.
Occurrences of the word is substituted with number and it acts as a pointer to the original occurrence

Text File Compression (continued)

Graphics File Compression
Run Length Encoding is a technique that looks for patterns (i.e.)blocks of same color.
Graphics file with .tif ,.gif, .pcx and .jpg contain bitmap images that have already been stored in compressed formats
Graphics software used to open and save files contains codes required to compress and decompress them.

Graphics File Compression (continued)
Compressed file Formats use
Lossy Compression
Lossless Compression

Lossy compression
Throws away some of the original data for the graphic
JPEG(Joint Photographic Experts Group)

Lossless compression
Lossless Compression provides a way to reconstitute all of the original data in a graphics file.

Photoshop File (PSD.PDD)
A Photoshop file
File is both a vector image and also a raster
Keep layers, layer masks and also the color like RGB
Max - 300,000 by 300,000 pixels per image

BMP (BMP.RLE.DIB)
A raster type of file
Made up of pixels
Only uses RGB colors
Cannot be used on WebPages
Have a large file size

JPEG (JPG.JPEG.JPE)
Raster file
Can be used for WebPages
A small file that can be uploaded on WebPages and it will be good quality
Support lots of color like RGB and CMYK.

Video File Compression
Used to display video on the PC by
Reducing number of frames displayed per second.
Number of frames per second affects the smoothness of the video.
High quality video displays 30 frames/sec and low quality 10-15/sec

Video File Compression (continued)
- Reducing the size of the video widow.
Displaying an image 1/4 of the screen requires only 1/4 of the data required to display on a screen.
Technique is termed Intra frame Compression
Coding only the changes that take place one frame to next
Difference between frames are evaluated and the data changed are stored.
Technique is termed motion compensation

Motion compensation