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Extend doc on dense+sparse

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Gael Guennebaud 2016-01-30 14:58:21 +01:00
parent 1bc207c528
commit 102fa96a96
1 changed files with 7 additions and 0 deletions
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7
doc/TutorialSparse.dox
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@ -257,7 +257,14 @@ Binary coefficient wise operators can also mix sparse and dense expressions:
\code
sm2 = sm1.cwiseProduct(dm1);
dm2 = sm1 + dm1;
dm2 = dm1 - sm1;
\endcode
Performance-wise, the adding/subtracting sparse and dense matrices is better performed in two steps. For instance, instead of doing <tt>dm2 = sm1 + dm1</tt>, better write:
\code
dm2 = dm1;
dm2 += sm1;
\endcode
This version has the advantage to fully exploit the higher performance of dense storage (no indirection, SIMD, etc.), and to pay the cost of slow sparse evaluation on the few non-zeros of the sparse matrix only.
%Sparse expressions also support transposition: