README.md

Solution

1. Matrix Sums

In hw4, we need to implement row_sums and column_sums. These two problems are quite easy.

__global__ void row_sums(const float *A, float *sums, size_t ds){

  int idx = threadIdx.x+blockDim.x*blockIdx.x; // create typical 1D thread index from built-in variables
  if (idx < ds){
    float sum = 0.0f;
    for (size_t i = 0; i < ds; i++)
      sum += A[idx*ds+i];         // write a for loop that will cause the thread to iterate across a row, keeeping a running sum, and write the result to sums
    sums[idx] = sum;
}}

__global__ void column_sums(const float *A, float *sums, size_t ds){

  int idx = threadIdx.x+blockDim.x*blockIdx.x; // create typical 1D thread index from built-in variables
  if (idx < ds){
    float sum = 0.0f;
    for (size_t i = 0; i < ds; i++)
      sum += A[i*ds + idx];         // write a for loop that will cause the thread to iterate down a column, keeeping a running sum, and write the result to sums
    sums[idx] = sum;
}}