colwise_sum()

template<typename T , require_all_kernel_expressions_t< T > * = nullptr>

auto stan::math::colwise_sum ( T &&  a )

inline

Column wise sum - reduction of a kernel generator expression.

So as to be efficient column wise reductions are only done partially. That means instead of 1 row kernel output will have a few rows that need to be reduced to obtain the final result (actually it is 1 result per work group run - roughly 16 times the number of compute units on the OpenCL device). This can be done in a separate kernel or after copying to CPU. Also column wise reductions can not be used as arguments to other operations - they can only be evaluated.

Template Parameters

T	type of input expression

Parameters

a	the expression to reduce

Returns

sum

Definition at line 224 of file colwise_reduction.hpp.