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Switched Matrix::collect() over to a memcpy, but the results weren't actually an improvement

release/4.3a0
Alex Cunningham 2010-01-20 01:42:36 +00:00
parent d2291a38d1
commit b860f06614
2 changed files with 18 additions and 6 deletions
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20
cpp/Matrix.cpp
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@ -505,12 +505,24 @@ Matrix collect(const std::vector<const Matrix *>& matrices, size_t m, size_t n)
dimA2 += M->size2();
}
Matrix A(dimA1, dimA2);
double * Aptr = A.data().begin();
size_t hindex = 0;
BOOST_FOREACH(const Matrix* M, matrices) {
for(size_t d1 = 0; d1 < M->size1(); d1++)
for(size_t d2 = 0; d2 < M->size2(); d2++)
A(d1, d2+hindex) = (*M)(d1, d2);
hindex += M->size2();
size_t row_len = M->size2();
// find the size of the row to copy
size_t row_size = sizeof(double) * row_len;
// loop over rows
for(size_t d1 = 0; d1 < M->size1(); ++d1) { // rows
// get a pointer to the start of the row in each matrix
double * Arow = Aptr + d1*dimA2 + hindex;
double * Mrow = const_cast<double*> (M->data().begin() + d1*row_len);
// do direct memory copy to move the row over
memcpy(Arow, Mrow, row_size);
}
hindex += row_len;
}
return A;

4
cpp/timeMatrix.cpp
View File

@ -14,8 +14,8 @@ using namespace gtsam;
/*
* Results:
* Alex's Machine:
* - no pass: 0.184 sec
* - pass : 0.181 sec
* - (1st pass of simple changes) no pass: 0.184 sec , pass: 0.181 sec
* - (1st rev memcpy) no pass: 0.181 sec , pass: 0.180 sec
*/
double timeCollect(size_t p, size_t m, size_t n, bool passDims, size_t reps) {
// create a large number of matrices