Databases
StackOverflow2013
Postsdbo
POperformance of multiplying 2 identical/nonidentical matrix
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POperformance of multiplying 2 identical/nonidentical matrix
    primarykey
    data
    text
    <p>I am carrying out some performance test on scientific application and trying to take into account all elements that can affect performance of application(like cache size hierarchy cpu speed ... cache line and what ever can be involve with performance). This question comes to my mind although it might be stupid one but i would like to make it obvious to me.</p> <p>*<strong><em>Question:</em>*</strong></p> <p>if I am not right correct me please.cost of processing int and float or double value is different on processor and that is because of using CPU floating point unit (to calculate floating point values) . Now I want to know if there is difference between filling two 2d matrix with the same float or double value and multiply them or fill them with random float or double value and then multiplying them. Dose compiler use cacheing for matrix which all elements have the same values?.</p> <p>Altogether processing processing floating value like (<strong>A.B</strong>) in which A and B can be numbers with different size in digits if size of A and B have any impact on processing time (for example multiplication) or not? and if there is a difference dose it important to consider it or not? . I am able to measure performance of my application using performance counter library but because of the overhead of used library you can not say for sure that Instruction/flops variation is for random value or other parameter like I/Dcache miss, cache size, problem size or other parameters.</p> <p>used machine intel E4500. compiler g++ 4.7.</p> <p>Thanks</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USmjr
    1. USmjr
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POperformance of multiplying 2 identical/nonidentical matrix
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI strongly doubt the compiler will cache the values. Some maths API, on the other hand, might. There's even a (probably slim) chance that the processor may. To benchmark, run it enough times or on a big enough matrix so that it actually takes at least a few seconds, and populate the matrix outside of the performance check.
      singulars
      1. POperformance of multiplying 2 identical/nonidentical matrix
      1. USDukeling
    2. COThis is why high-level optimisations are more important than low-level optimisations. If you know that all the values are the same, you can reduce the problem from O(n^3) to O(n^2), whereas no matter how smart the processor is, it will always be O(n^3) if you perform the full multiplication.
      singulars
      1. POperformance of multiplying 2 identical/nonidentical matrix
      1. USOmri Barel
    3. COYour question is really general. Can you be more specific as to the circumstances? Mentioning all possible optimizations across the entire stack is almost impossible in such a general case.
      singulars
      1. POperformance of multiplying 2 identical/nonidentical matrix
      1. USEamon Nerbonne
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload