R/acmtf_fg.R

In CMTFtoolbox: Create (Advanced) Coupled Matrix and Tensor Factorization Models

#' Function value and gradient calculation for ACMTF
#'
#' @param x Vectorized parameters of the CMTF model.
#' @param Z Z object as generated by [setupCMTFdata()].
#' @param alpha Alpha value of the loss function as specified by Acar et al., 2014
#' @param beta Beta value of the loss function as specified by Acar et al., 2014
#' @param epsilon Epsilon value of the loss function as specified by Acar et al., 2014
#'
#' @return A list containing the function ("fn") and the gradient ("gr").
#' @export
#'
#' @examples
#' A = array(rnorm(108*2), c(108, 2))
#' B = array(rnorm(100*2), c(100, 2))
#' C = array(rnorm(10*2), c(10, 2))
#' D = array(rnorm(100*2), c(100,2))
#' E = array(rnorm(10*2), c(10,2))
#'
#' df1 = reinflateTensor(A, B, C)
#' df2 = reinflateTensor(A, D, E)
#' datasets = list(df1, df2)
#' modes = list(c(1,2,3), c(1,4,5))
#' Z = setupCMTFdata(datasets, modes, normalize=FALSE)
#'
#' init = initializeACMTF(Z, 2, output="vect")
#' outcome = acmtf_fg(init, Z)
#' f = outcome$fn
#' g = outcome$gr
acmtf_fg = function(x, Z, alpha=1, beta=rep(1e-3, length(Z$object)), epsilon=1e-8){

  numDatasets = length(Z$object)
  numModes = max(unlist(Z$modes))
  Fac = vect_to_fac(x, Z)
  numComponents = ncol(Fac[[1]])

  # Precalculate the reinflated blocks
  reinflatedBlocks = reinflateFac(Fac, Z, returnAsTensor=TRUE)

  # Precalculate the residuals of the blocks
  residuals = list()
  for(p in 1:numDatasets){
    reinflatedBlock = reinflatedBlocks[[p]]
    residualBlock = Z$object[[p]] - reinflatedBlock
    residuals[[p]] = Z$missing[[p]] * residualBlock
  }

  ## LOSS PART ##

  # Penalty for fit on X
  f_per_term = rep(NA, numDatasets)
  for(p in 1:numDatasets){
    Fnorm = rTensor::fnorm(residuals[[p]]) # verified to work for matrices too
    f_per_term[p] = 0.5 * Fnorm^2
  }

  # Penalty to make the solution norm 1
  f_norm = matrix(NA, nrow=numModes, ncol=numComponents)
  for(i in 1:numModes){
    for(j in 1:numComponents){
      f_norm[i,j] = 0.5 * alpha * (norm(as.matrix(Fac[[i]][,j]), "2")-1)^2
    }
  }

  # Penalty on the lambdas
  f_lambda = matrix(NA, nrow=numComponents, ncol=numDatasets)
  for(i in 1:numComponents){
    for(p in 1:numDatasets){
      lambda_r = Fac[[numModes+1]][p,i]
      f_lambda[i,p] =  0.5 * beta[p] * (sqrt(lambda_r^2 + epsilon))
    }
  }

  f = sum(f_per_term) + sum(f_norm) + sum(f_lambda)

  ## GRADIENT PART ##
  gradient = list()

  # Gradients per mode stored in a list, will be vectorized at the end.
  for(i in 1:numModes){
    gradient[[i]] = array(0L, dim(Fac[[i]]))

    # Gradient as generated per dataset
    # Note: this is different from CMTF because it multiplies the residuals by the lambdas
    for(p in 1:numDatasets){
      modes = Z$modes[[p]]

      if(i %in% modes){
        idx = which(modes==i)
        otherModes = modes[-idx]

        unfoldedX = rTensor::k_unfold(Z$missing[[p]], idx) * rTensor::k_unfold(Z$object[[p]], idx)
        unfoldedXhat = rTensor::k_unfold(Z$missing[[p]], idx) * rTensor::k_unfold(reinflatedBlocks[[p]], idx)
        lambdas = Fac[[numModes+1]][p,]

        if(length(modes) == 3){
          gradientMode = (unfoldedXhat - unfoldedX)@data %*% multiway::krprod(t(lambdas), multiway::krprod(Fac[[otherModes[2]]], Fac[[otherModes[1]]]))
        } else if(length(modes) == 2){
          gradientMode = (unfoldedXhat - unfoldedX)@data %*% Fac[[otherModes[1]]] %*% diag(x=lambdas, nrow=length(lambdas), ncol=length(lambdas))
        }
        else{
          stop(paste0("Number of modes is incorrect for block ", p))
        }

        gradient[[i]] = gradient[[i]] + gradientMode
      }
    }

    # Gradient of norm 1 restriction
    gradient[[i]] = gradient[[i]] + alpha * (Fac[[i]] - removeTwoNormCol(Fac[[i]]))
  }

  # Gradient of the lambdas
  gradient[[numModes+1]] = array(0L, dim(Fac[[numModes+1]]))
  for(i in 1:numDatasets){
    modes = Z$modes[[i]]

    for(j in 1:numComponents){
      lambda_r = Fac[[numModes+1]][i,j]
      residuals = reinflatedBlocks[[i]] - Z$object[[i]]
      residuals = Z$missing[[i]] * residuals

      for(k in 1:length(modes)){
        residuals = rTensor::ttm(residuals, t(as.matrix(Fac[[modes[k]]][,j])), k)
      }

      gradient[[numModes+1]][i,j] = residuals@data[1] + ((beta[i]/2) * (lambda_r / (sqrt(lambda_r^2+epsilon))))
    }
  }

  g = fac_to_vect(gradient)
  return(list("fn"=f, "gr"=g))
}