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c++eigensimd
Thomas
Thomas

Reputation: 6196

bitwise operations in Eigen

It doesn't seem like Eigen supports bitwise operations.

I would like bitwise SIMD functionality for "shift left" and "and".

Is there a quick and dirty way to implement this functionality? Can i call an intrinsic function and input it with something like Eigen vector.data()?

Upvotes: 3

Views: 1483

Answers (2)

Paul Price
Paul Price

Reputation: 2787

You could use the unaryExpr and binaryExpr methods. Here's an example of summing array values where the corresponding mask matches the desired bitmask:

// 'mask' is an Eigen matrix of type an integer type (MaskT).
// 'values' is an Eigen matrix of floating-point type.
// 'bitmask' is of an integer type (MaskT).
auto const select = mask.unaryExpr(
    [bitmask](MaskT value) { return value & bitmask; }
).template cast<bool>();
double const sum = select.select(values.template cast<double>(), 0.0).sum();

Upvotes: 0

Tal
Tal

Reputation: 357

I think Eigen don't support this because that there isn't a good way to do this for float, double and complex numbers.

You can always override those C++ bitwise operators by yourself, taking two MatrixBase as parameters.

For bitwise assignment operators, you need to add a function inside MatrixBase class. Eigen made this possible, see here how to.

Upvotes: 2

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