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3
votes
1answer
24 views

Bare Metal Operating Systems in High Performance Computing

Few years back, I stumbled across Return Infinity - the OS framework designed around flat, 64bit memory model, with minimal MMU / VM overhead, etc. I'm wondering if there are any public benchmarks or ...
10
votes
5answers
20 views

Why is the OS design able to reduce power consumption?

I have read that OSes like Android and iOS are somehow optimised to improve battery life. My understanding is that a CPU executes a certain number of operations in a certain time, so I would think ...
7
votes
1answer
19 views

Why using Hyper-threading can lead to performance degradation

I have read it at various places like this, that Hyper-threading leads to performance degradation. I am unable to get why or how hyper-threading leads to degradation. Why it is so that even when ...
8
votes
1answer
20 views

Performance of microkernel vs monolithic kernel

A microkernel implements all drivers as user-space programs, and implements core features like IPC in the kernel itself. A monolithic kernel, however, implements the drivers as a part of the kernel ...
2
votes
0answers
81 views

What is the average-case running time of Fun-sort?

I read this paper: http://www.sciencedirect.com/science/article/pii/S0166218X04001131?np=y (you can check the PDF online for free), and I translated section 4's Fun-sort algorithm (correct me if I'm ...
3
votes
2answers
76 views

Why is the throughput (performance) of the Slotted Aloha protocol ≈ 0.36

I've read that the throughput - that is, the amount of good useful messages relative to capacity - of the Slotted ALOHA protocol for communication networks is roughly 0.36%. But its not clear how we ...
2
votes
1answer
112 views

Why is the throughput (performance) of the Aloha protocol ≈ 0.18?

I've read in a few places (like here that the throughput - that is, the amount of good useful messages relative to capacity - of the ALOHA protocol for networks is roughly 0.18%. But its not clear ...
1
vote
1answer
81 views

Definition of “c-competitive” algorithm

What is the definition of a "c-competitive" algorithm? For example what does it mean, if we say that there is a 2-competitive algorithm for packet routing?
0
votes
1answer
82 views

How do people measure performance overhead?

How do people measure performance overhead? Whenever someone is bragging about how their program or application performs better than another, they talk about particular measurements, eg time, ...
0
votes
2answers
107 views

Quicksort's asymptotic performance for array of [50,…,50,100,…100]

Let's have an array where first half are of value 50 and the second half 100. What would be the asymptotic performance when sorting using Quicksort. I think it it should be $O(n^2)$ as for array of ...
1
vote
1answer
60 views

The theoretical upper bounds for duplicate detection in a set of objects?

I recently had a lengthy exchange with someone about the most efficient way to remove duplicates from a collection. The debate was mostly centered around the specific behavior of C# collections, such ...
6
votes
2answers
487 views

Fast hashing: combination of different techniques to identify changes in a file?

I want to create a fast way to detect whether a file might or might not be the same. For almost 100% sureness I would use an existing hash algorithm, e.g. SHA256. However, the files are expected to be ...
0
votes
1answer
64 views

Task Manager Performance tab in windows [closed]

I do not understand the following options in windows. Could any one explain
4
votes
2answers
134 views

How to avoid column wise access in matrix multiplication?

I know when we access elements in rows it will be much faster than if it is accessed column wise. In matrix multiplication one of the matrices must be accessed column wise. In GPUs with CUDA/OpenCL ...
0
votes
0answers
28 views

Applications affected by memory performance

I'm writing a paper on the topic of applications affected more by memory performance than processor performance. I've got a lot written regarding the gap between the two, however I can't seem to find ...
2
votes
1answer
141 views

Tree flattening with layout guarantees

I want to flatten a binary tree into a linear array, and I wonder if there are specific algorithms to improve locality in the linearized representation (for instance, ensuring that all data from the ...
4
votes
1answer
367 views

Performance of row- vs. column-wise matrix traversal

Scott Meyers describes here that traversing a symmetric matrix row-wise performes significantly better over traversing it column-wise - which is also significantly counter-intuitive. The reasoning ...
0
votes
0answers
26 views

What are these notations O(1)/O(n)/O(log n)? [duplicate]

I am a newbie here I recently read tutorials on java about collection framework. The time complexity of various objects in reading/writing data What does it mean? ...
0
votes
2answers
128 views

What does it mean when a computer runs 'faster'?

If you have two computers with only one thread, a and b. And computer a runs twice as fast as computer b. Does this mean that computer a and can do twice as many operations in a given time in ...
5
votes
1answer
186 views

Is the memory-runtime tradeoff an equivalent of Heisenberg's uncertainty principle?

When I work on an algorithm to solve a computing problem, I often experience that speed can be increased by using more memory, and memory usage can be decreased at the price of increased running time, ...
2
votes
2answers
128 views

Regarding to the speed of supercomputer

There seems to be a sense of competition in creating the fastest computer in the world, and I feel like technically you just have to continue increasing the core number to gain more flops, which is ...
2
votes
1answer
72 views

performance between the data structures

I have developed two existing data structures and I want to see their performances over a certain algorithm. In this case I use Dijkstra's algorithm with binary and Fibonacci heaps. Just to ask, if I ...
0
votes
1answer
21 views

VAR autoincrement with constant space consumption for super large tables

Assume there was a database system that had a data type called VARINT or some variant that allowed instead of fixed-length INTs ...
2
votes
1answer
50 views

Optimization of Hierarchical Data Propagation

I have a system in existence which works on parent-child model. They share common attributes, as they belong to same class. A parent can enforces certain data on any user selected attribute, and the ...
8
votes
3answers
560 views

Finding maximum and minimum of consecutive XOR values

Given an integer array (maximum size 50000), I have to find the minimum and maximum $X$ such that $X = a_p \oplus a_{p+1} \oplus \dots \oplus a_q$ for some $p$, $q$ with $p \leq q$. I have tried this ...
-1
votes
2answers
128 views

How to determine the Utilization and Efficiency of a file server?

I have shown my work below for the problem and would appreciate if someone can let me know if I'm on the right track or point me in the right direction if not. An 8 processor file server handles a ...
2
votes
0answers
52 views

Determine interference factors in parallel computing

Parallel processes interfere with each other in many ways, by competing for shared resources such as shared caches, memory, disks, etc. Would it be possible to determine latent factors just with a ...
1
vote
0answers
31 views

How to generate inputs to evaluate the performance of an implementation?

How can we assert that the performance of an implementation matches the expected performance defined in terms of Big-$\mathcal{O}$ and friends by generating best/worst case inputs? I'm thinking of a ...
2
votes
1answer
1k views

Theoretical speed gain of quad core vs. single core

I first asked this question at cstheory, but they suggested to ask my question here, so here it goes ... I'm working on my masters thesis and I need to have theoretical value of the (average) speed ...
6
votes
3answers
3k views

A faster, leaner JavaScript for scientific computing: what features should I keep?

Here I'm really interested in lowering barriers to mathematical education. Target: I'd like to see created for the JavaScript community, an equivalent of the Python-based/linked scientific and ...