Vector-transposing functionUsage of a C library in a C++ project (std::string char array conversion)Speeding...
PTIJ: Mouthful of Mitzvos
Called into a meeting and told we are being made redundant (laid off) and "not to share outside". Can I tell my partner?
Can a Mexican citizen living in US under DACA drive to Canada?
Convert an array of objects to array of the objects' values
Can you run a ground wire from stove directly to ground pole in the ground
Rationale to prefer local variables over instance variables?
Searching for a string that contains the file name
What is Tony Stark injecting into himself in Iron Man 3?
The need of reserving one's ability in job interviews
How can friction do no work in case of pure rolling?
Linear Combination of Atomic Orbitals
What is "desert glass" and what does it do to the PCs?
The past tense for the quoting particle って
Why dativ case for the verb widerspricht?
Is there a way to find out the age of climbing ropes?
Who is at the mall?
Ultrafilters as a double dual
Are there other characters in the Star Wars universe who had damaged bodies and needed to wear an outfit like Darth Vader?
How to make sure I'm assertive enough in contact with subordinates?
A bug in Excel? Conditional formatting for marking duplicates also highlights unique value
Naming Characters after Friends/Family
Named nets not connected in Eagle board design
How spaceships determine each other's mass in space?
Align equations with text before one of them
Vector-transposing function
Usage of a C library in a C++ project (std::string char array conversion)Speeding up and shortening a loopSieve of Eratosthenes - segmented to increase speed and rangeRandom class in C++Calculating the determinant of a matrixA library to do maths with matrices written from scratchPitch detection library, basic architectureUndirected Unweighted Graph Implementation - C++Solving the game WordBrain using brute forceNon generic Skip List implementation in C++ Version 2
$begingroup$
I profiled a library I'm writing that uses vector transposes and found that I am spending a good bit of time doing the following transpose. I am using a std::vector of std::vector<double>s to represent the column vectors.
What are some ways to optimize this function?
std::vector<double> transpose_vector(const std::vector<std::vector<double>> &column_vec) {
// take a column vector:
// |x1|
// |x2|
// |x3|
// and return a row vector |x1, x2, x3|
std::vector<double> row_vector;
for (auto c : column_vec) {
for (auto r : c) {
row_vector.push_back(r);
}
}
return row_vector;
}
c++ performance c++11 vectors
edited 2 mins ago
200_success
130k16153419
asked 56 mins ago
L LL L
405
$endgroup$
add a comment |
$begingroup$
I profiled a library I'm writing that uses vector transposes and found that I am spending a good bit of time doing the following transpose. I am using a std::vector of std::vector<double>s to represent the column vectors.
What are some ways to optimize this function?
std::vector<double> transpose_vector(const std::vector<std::vector<double>> &column_vec) {
// take a column vector:
// |x1|
// |x2|
// |x3|
// and return a row vector |x1, x2, x3|
std::vector<double> row_vector;
for (auto c : column_vec) {
for (auto r : c) {
row_vector.push_back(r);
}
}
return row_vector;
}
c++ performance c++11 vectors
edited 2 mins ago
200_success
130k16153419
asked 56 mins ago
L LL L
405
$endgroup$
add a comment |
$begingroup$
I profiled a library I'm writing that uses vector transposes and found that I am spending a good bit of time doing the following transpose. I am using a std::vector of std::vector<double>s to represent the column vectors.
What are some ways to optimize this function?
std::vector<double> transpose_vector(const std::vector<std::vector<double>> &column_vec) {
// take a column vector:
// |x1|
// |x2|
// |x3|
// and return a row vector |x1, x2, x3|
std::vector<double> row_vector;
for (auto c : column_vec) {
for (auto r : c) {
row_vector.push_back(r);
}
}
return row_vector;
}
c++ performance c++11 vectors
edited 2 mins ago
200_success
130k16153419
asked 56 mins ago
L LL L
405
$endgroup$
I profiled a library I'm writing that uses vector transposes and found that I am spending a good bit of time doing the following transpose. I am using a std::vector of std::vector<double>s to represent the column vectors.
What are some ways to optimize this function?
std::vector<double> transpose_vector(const std::vector<std::vector<double>> &column_vec) {
// take a column vector:
// |x1|
// |x2|
// |x3|
// and return a row vector |x1, x2, x3|
std::vector<double> row_vector;
for (auto c : column_vec) {
for (auto r : c) {
row_vector.push_back(r);
}
}
return row_vector;
}
c++ performance c++11 vectors
c++ performance c++11 vectors
edited 2 mins ago
200_success
130k16153419
asked 56 mins ago
L LL L
405
edited 2 mins ago
200_success
130k16153419
asked 56 mins ago
L LL L
405
edited 2 mins ago
200_success
130k16153419
edited 2 mins ago
200_success
130k16153419
edited 2 mins ago
200_success
130k16153419
130k16153419
asked 56 mins ago
L LL L
405
asked 56 mins ago
L LL L
405
asked 56 mins ago
L LL L
405
405
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
There's not really much here. The only thing I can think of is it may prove faster to pre-allocate the destination vector using reserve. push_back has the potential to cause several re-allocations per call to transpose, which will be slow. Try:
std::vector<double> transpose_vector(const std::vector<std::vector<double>> &column_vec) {
std::vector<double> row_vector;
row_vector.reserve(total_entries(column_vec)); // Pre-allocate the space we need
for (auto c : column_vec) {
for (auto r : c) {
row_vector.push_back(r);
}
}
return row_vector;
}
Where total_entries is a function that finds how many cells there are in the 2D vector. If each row is the same length, you could use math to figure this out. If it's ragged though, you may need to iterate column_vector summing the row lengths.
answered 31 mins ago
CarcigenicateCarcigenicate
3,62211631
$endgroup$
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["\$", "\$"]]);
});
});
}, "mathjax-editing");
StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "196"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fcodereview.stackexchange.com%2fquestions%2f214971%2fvector-transposing-function%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
There's not really much here. The only thing I can think of is it may prove faster to pre-allocate the destination vector using reserve. push_back has the potential to cause several re-allocations per call to transpose, which will be slow. Try:
std::vector<double> transpose_vector(const std::vector<std::vector<double>> &column_vec) {
std::vector<double> row_vector;
row_vector.reserve(total_entries(column_vec)); // Pre-allocate the space we need
for (auto c : column_vec) {
for (auto r : c) {
row_vector.push_back(r);
}
}
return row_vector;
}
Where total_entries is a function that finds how many cells there are in the 2D vector. If each row is the same length, you could use math to figure this out. If it's ragged though, you may need to iterate column_vector summing the row lengths.
answered 31 mins ago
CarcigenicateCarcigenicate
3,62211631
$endgroup$
add a comment |
$begingroup$
There's not really much here. The only thing I can think of is it may prove faster to pre-allocate the destination vector using reserve. push_back has the potential to cause several re-allocations per call to transpose, which will be slow. Try:
std::vector<double> transpose_vector(const std::vector<std::vector<double>> &column_vec) {
std::vector<double> row_vector;
row_vector.reserve(total_entries(column_vec)); // Pre-allocate the space we need
for (auto c : column_vec) {
for (auto r : c) {
row_vector.push_back(r);
}
}
return row_vector;
}
Where total_entries is a function that finds how many cells there are in the 2D vector. If each row is the same length, you could use math to figure this out. If it's ragged though, you may need to iterate column_vector summing the row lengths.
answered 31 mins ago
CarcigenicateCarcigenicate
3,62211631
$endgroup$
add a comment |
$begingroup$
There's not really much here. The only thing I can think of is it may prove faster to pre-allocate the destination vector using reserve. push_back has the potential to cause several re-allocations per call to transpose, which will be slow. Try:
std::vector<double> transpose_vector(const std::vector<std::vector<double>> &column_vec) {
std::vector<double> row_vector;
row_vector.reserve(total_entries(column_vec)); // Pre-allocate the space we need
for (auto c : column_vec) {
for (auto r : c) {
row_vector.push_back(r);
}
}
return row_vector;
}
Where total_entries is a function that finds how many cells there are in the 2D vector. If each row is the same length, you could use math to figure this out. If it's ragged though, you may need to iterate column_vector summing the row lengths.
answered 31 mins ago
CarcigenicateCarcigenicate
3,62211631
$endgroup$
There's not really much here. The only thing I can think of is it may prove faster to pre-allocate the destination vector using reserve. push_back has the potential to cause several re-allocations per call to transpose, which will be slow. Try:
std::vector<double> transpose_vector(const std::vector<std::vector<double>> &column_vec) {
std::vector<double> row_vector;
row_vector.reserve(total_entries(column_vec)); // Pre-allocate the space we need
for (auto c : column_vec) {
for (auto r : c) {
row_vector.push_back(r);
}
}
return row_vector;
}
Where total_entries is a function that finds how many cells there are in the 2D vector. If each row is the same length, you could use math to figure this out. If it's ragged though, you may need to iterate column_vector summing the row lengths.
answered 31 mins ago
CarcigenicateCarcigenicate
3,62211631
answered 31 mins ago
CarcigenicateCarcigenicate
3,62211631
answered 31 mins ago
CarcigenicateCarcigenicate
3,62211631
answered 31 mins ago
CarcigenicateCarcigenicate
3,62211631
3,62211631
add a comment |
add a comment |
Thanks for contributing an answer to Code Review Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fcodereview.stackexchange.com%2fquestions%2f214971%2fvector-transposing-function%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown