All Questions
15 questions
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84
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Why is my OpenMP based Code not getting any speedup?
I am trying to fill in "valid points" into a vector of vectors and I do it with the use of local vector of vector which I then merge. I also write the time measuring strategy for ...
- 29
0
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0
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55
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does this triply nested do loop produce false sharing in OpenMP Fortran?
I am trying to parallelize a code I inherited from someone.
I am still learning about OpenMP.
I know that if multiple threads bounce back and fort a cache line and at least one of them writes to it, ...
- 566
0
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0
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119
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How to use #pragma omp task with #pragma omp simd
I want to write a parallel program that computes a perimeter, area and diagonal of multiple rectangles. The way I thought is to use a functional parallelism to build my program.
First, the perimeter, ...
0
votes
1
answer
244
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OpenMP parallel for does not speed up array sum code [duplicate]
I'm trying to test the speed up of OpenMP on an array sum program.
The elements are generated using random generator to avoid optimization.
The length of array is also set large enough to indicate the ...
- 461
0
votes
2
answers
389
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OpenMP. Parallelization of two consecutive cycles
I am studying OpenMP and have written an implementation of shaker sorting. There are 2 consecutive cycles here, and in order for them to be called sequentially, I added blockers in the form of ...
- 123
1
vote
2
answers
269
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OpenMP. Parallelization of the loop in N threads
I am trying to parallelize a cycle of 50 million iterations with several threads - first by 1, then by 4, 8 and 16. Below is the code for implementing this functionality.
#include <iostream>
#...
- 123
1
vote
2
answers
71
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How does OpenMP actually reduce clock cycles?
It might be a silly question but, with OpenMP you can achieve to distribute the number of operations between all the cores your CPU has. Of course, it is going to be faster in 99% times because you ...
- 99
2
votes
1
answer
1k
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Efficient Parallel algorithm for array filtering
Given a very large array I want to select only the elements that match some condition. I know a priori the number of elements that will be matched. My current pseucode is:
filter(list):
out = list ...
0
votes
1
answer
272
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Concurrent update to dynamic array in C with OpenMP
Suppose many threads try to append elements at the end of a dynamically allocated array. If there is not enough room, the array must be reallocated, but then its address in memory may change, and ...
1
vote
2
answers
266
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Execution time goes up the more threads I use OpenMP, what's wrong?
I have written a program that takes in a dictionary and finds all the words in the dictionary that are palindromes. I have attempted to parallelize the going through of this dictionary, and the ...
- 103
-1
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1
answer
52
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How to configure g++ so that x++ is atomic (Ubuntu, openmp)?
I have a simple instruction cout << x++ that is concurrently executed by my threads. I sorted the output then did a uniq-c and indeed the counts are greater than 1 for many values. So that ...
- 1,303
0
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1
answer
170
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omp parallel doesn't give any performance increase for matrix multiplication
I'm using following 2 code blocks to compute matrix multiplication serially and parallel.
Serial -
double** ary1 = new double*[in];
double** ary2 = new double*[in];
double** result = new double*[in]...
- 1,961
2
votes
1
answer
1k
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How to parallel nested loop to find the nearest two point in OpenMP? [duplicate]
This question is not a duplicate of fusing nested loops. The OP wants to do a reduction of a maximum value and at the same time store two indices. Fusing the loops will not fix the OPs problem. The OP ...
- 3,653
5
votes
3
answers
4k
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OpenMP Parallel for-loop showing little performance increase
I am in the process of learning how to use OpenMP in C, and as a HelloWorld exercise I am writing a program to count primes. I then parallelise this as follows:
int numprimes = 0;
#pragma omp ...
- 12.6k
6
votes
3
answers
8k
views
Microsoft Parallel Patterns Library (PPL) vs. OpenMP
I want to compare PPL vs. OpenMP regarding their performance, but can't find a detailed investigation on the web. I believe there are not many people who are experienced with PPL.
I'm developing my ...
- 868