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The subdirectory norm contains a skeletons for a thrust-based algorithm for computing the two-norm of a vector.

Documentation for thrust can be found at https://docs.nvidia.com/cuda/thrust/index.html

|d_| Complete the implementation of the norm_thrust function in norm_thrust.cu. |_d|

You may find it helpful to refer to the axpy examples for the rest of this problem. In cu_axpy_t, we used thrust::transform to combine two vectors. To compute the norm of a single vector, we want an analagous operation – transforming over a single vector. We also want to reduce (accumulate) over the transformed values (and we know how to do that efficiently – per the reduction exercise – and there is a reduce function in thrust).

We could do this in two steps – transform the vector into a vector with the square of each value and the reduce over that. That approach is obviously enormously inefficient. To do the transformation and reduction in a single pass, thrust includes the function transform_reduce – which is suggested for use in this problem. You may use any technique you like to implement the operators that get passed in – function object, helper function, lambda, built-in functions.

The norm_cuda subdirecory also contains norm_parfor and norm_seq, which you can run to compare to norm_cuda.

Note that norm_thrust is a function template. The driver that calls it for timing invokes to versions of it – one for single precision and one for double precision.

As with our previous norm drivers, this program will run timing tests over a range of problem sizes (in powers of two) and you can pass the upper and lower bounds in on the command line. The program does two timing runs for each of single and double and prints the results.

$./norm_thrust.exe

Float
        N  Sequential       First      Second       First      Second
  1048576      1.7798     6.09445     6.07604    2.7595e-08    2.7595e-08
  2097152     1.68752      11.108     11.2314   4.51044e-08   4.51044e-08
  4194304     1.41257     18.6075     19.1292   2.15465e-08   2.15465e-08
  8388608     1.38701     27.5941     29.5374   3.51608e-08   3.51608e-08
 16777216     1.38567     36.9667     45.4383   4.24208e-08   4.24208e-08
 33554432     1.37679     41.2072     57.2881   8.84264e-09   8.84264e-09
 67108864     1.38583     29.4984     65.4721   2.65331e-09   2.65331e-09

Double
        N  Sequential       First      Second       First      Second
  1048576     1.78137     6.38466     6.44605   1.36909e-11   1.36909e-11
  2097152     1.69176     11.0473     11.0473   2.58195e-11   2.58195e-11
  4194304     1.41943     17.2002     17.3459   1.87745e-12   1.87745e-12
  8388608     1.39531     24.1052     24.1052   8.97525e-12   8.97525e-12
 16777216     1.39186     29.8772     29.8772   6.11285e-13   6.11285e-13
 33554432     1.38983     33.5544     34.0407    2.9634e-12    2.9634e-12
 67108864     1.38298     36.2751     36.2751   1.04758e-11   1.04758e-11

$ rsync -avuzb ps6 klone.hyak.uw.edu: