Speed u p : P a r a l l e l vs Seq u e n t i a l Code in .NET

Generation Code128 in .NET Speed u p : P a r a l l e l vs Seq u e n t i a l Code
Speed u p : P a r a l l e l vs Seq u e n t i a l Code
Code 128 Code Set A Generator In VS .NET
Using Barcode generator for .NET framework Control to generate, create Code 128B image in Visual Studio .NET applications.
number of processors, but slowdown at some point: for example, a parallel algorithm may not break even with a sequential algorithm until 4 processors have been applied and will scale well beyond this This could be due to con stant overheads introduced by parallelism that dwarf the advantages with small degrees of parallelism The same is true of using too many processors It could be that a parallel algorithm exhibits too much interthread commu nication and / or memory contention that end up dominating execution time when higher numbers of processors are used Most properly written parallel algorithms exhibit sublinear speedup The lack of perfect linear speedups is often due to the added costs of paral lelism and natural scaling inhibitors such as interthread communication For example, the parallel merge sort we examined in the previous chapter had a portion that was only moderately parallel and required communication the merge-which will prevent us from seeing a perfect linear speedup Moreover, a linear speedup of exactly P (without rounding) is highly unlikely; more often than not, the speedup will fall on one side or the other And, more often than not, the speedup will fall on the sublinear side At first, superlinear speedups may appear to be impossible How is it possible that, by applying P processors, some bit of code can execute more than P times as fast There are two basic ways in which this can happen (see further Reading, Sutter)
Decoding ANSI/AIM Code 128 In VS .NET
Using Barcode scanner for .NET Control to read, scan read, scan image in .NET applications.
Do more work in less time Use more resources that could only be utilized by doing so in parallel
Bar Code Drawer In .NET
Using Barcode creation for VS .NET Control to generate, create bar code image in VS .NET applications.
The first way, do more work in less time, seems like an obvious way to make any code go faster But parallelism can help in a unique way because multiple threads may be sharing information with one another This is normally exploited in search style algorithms To illustrate, imagine we are searching an array for a single element that has some particular criteria Perhaps evaluating an element against these criteria involves running a fairly complicated algorithm, such as some alpha-beta pruning game search As we go, we may decide to skip certain elements because they are similar (or identical) to other elements found to
Bar Code Scanner In .NET
Using Barcode reader for .NET Control to read, scan read, scan image in .NET framework applications.
C h a pter l it : Perfo r m a n ce a n d Sca la b i l i ty
Code 128 Code Set C Generator In C#
Using Barcode generation for .NET Control to generate, create Code 128 Code Set C image in VS .NET applications.
have been disqualified Each thread takes its own chunk of the input array to work on in parallel; for simplicities sake, we'll say there are N elements in the array, P threads, and each thread takes a contiguous chunk of N / P elements t o work o n b y itself Here is the key insight: by sharing the disqualifications, some threads may do less work than they would have done sequentially because of the way the list has been traversed If thread P finds that elements with certain properties are disqualified, it lets threads 0 P-1 know about that and they can skip any similar occurrences that they run across Less input needs to be examined than if we had simply walked the list sequentially The second way, use more resources which could only be utilized by doing so in parallel, applies to many kinds of resources The basic point is that instead of using one resource first, processing the results, moving on to the next, and so on, it is sometimes possible to use more resources at once This is similar to the way that multiple ALUs can be used in superscalar execution One kind of resource that immediately comes to mind is processor caches Because each processor has some private cache, a parallel algorithm can use more cache at once (across the machine) than the sequential version could This can lead to superlinear speedup
Code 128B Creator In .NET
Using Barcode generator for ASP.NET Control to generate, create ANSI/AIM Code 128 image in ASP.NET applications.
Efficiency: NlIturlll SClIlllblllty versus Speedups
Draw Code 128 Code Set C In Visual Basic .NET
Using Barcode generator for .NET framework Control to generate, create USS Code 128 image in .NET applications.
Placing speedups into the four buckets is useful for theoretical analysis but is not always sufficient There is a big difference between achieving a speedup of 2 on a 32-processor machine and a speedup of 30, and yet both are lumped together into the single sublinear category Addition ally, both values are absolute and depend greatly on the specific value of P, while we are often more interested in the natural scalability of an algorithm The parallel efficiency of an algorithm can be calculated by dividing the speedup by the number of processors: Efficiency Speedup / Po With this new metric, we can rephrase the definitions of our sublinear, linear, and superlinear categories 1 Efficiency < 1 indicates a sublinear speedup 2 Efficiency of exactly 1 indicates a linear speedup 3 Efficiency > 1 indicates a superlinear speedup
Printing EAN-13 In .NET
Using Barcode generation for .NET Control to generate, create UPC - 13 image in .NET framework applications.
Creating Bar Code In Visual Studio .NET
Using Barcode creator for Visual Studio .NET Control to generate, create bar code image in .NET applications.
GTIN - 128 Drawer In VS .NET
Using Barcode maker for Visual Studio .NET Control to generate, create EAN 128 image in .NET applications.
Creating DataMatrix In Visual C#
Using Barcode drawer for Visual Studio .NET Control to generate, create Data Matrix ECC200 image in VS .NET applications.
Generating Code 128 Code Set A In Visual C#.NET
Using Barcode creator for .NET framework Control to generate, create Code 128B image in Visual Studio .NET applications.
Barcode Drawer In .NET Framework
Using Barcode generator for ASP.NET Control to generate, create barcode image in ASP.NET applications.
Encode Bar Code In Java
Using Barcode drawer for Java Control to generate, create barcode image in Java applications.