R/199_reductions_dgp2dcp_canonicalizers_mulexpression_canon.R

In CVXR: Disciplined Convex Optimization

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## DO NOT EDIT THIS FILE!! EDIT THE SOURCE INSTEAD: rsrc_tree/reductions/dgp2dcp/canonicalizers/mulexpression_canon.R
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## CVXPY SOURCE: reductions/dgp2dcp/canonicalizers/mulexpression_canon.py
## DGP canonicalizer for MulExpression (matmul): log_sum_exp of inner products

.dgp_mulexpression_canon <- function(expr, args) {
  lhs <- args[[1L]]
  rhs <- args[[2L]]
  promoted <- mul_shapes_promote(lhs@shape, rhs@shape)
  lhs_shape <- promoted[[1L]]
  rhs_shape <- promoted[[2L]]
  lhs <- reshape_expr(lhs, lhs_shape)
  rhs <- reshape_expr(rhs, rhs_shape)

  rows <- list()
  for (i in seq_len(lhs_shape[1L])) {
    row <- list()
    for (j in seq_len(rhs_shape[2L])) {
      elems <- lapply(seq_len(lhs_shape[2L]), function(k) {
        lhs[i, k] + rhs[k, j]
      })
      arr <- do.call(hstack, elems)
      row <- c(row, list(log_sum_exp(arr)))
    }
    rows <- c(rows, list(row))
  }
  mat <- bmat(rows)
  if (!identical(mat@shape, expr@shape)) {
    mat <- reshape_expr(mat, expr@shape)
  }
  list(mat, list())
}