library(tidyverse)
library(magrittr)
library(shiny)
library(foreach)
library(iterators)
options(shiny.suppressMissingContextError=TRUE)
makeReactiveBinding("nodeA")
nodeA$in_1 <- NULL
nodeA$in_2 <- NULL
nodeA$out <- reactive(nodeA %$% (in_1 + in_2))
makeReactiveBinding("nodeB")
nodeB$in_1 <- reactive(nodeA$out())
nodeB$in_2 <- NULL
nodeB$out <- reactive(nodeB %$% (in_1() + in_2))
makeReactiveBinding("nodeC")
nodeC$in_1 <- reactive(nodeB$out())
nodeC$in_2 <- NULL
nodeC$out <- reactive(nodeC %$% (in_1() * in_2))
df <- tidyr::expand_grid(val1 = 0:5, val2 = 0:5, val3 = 0:5, val4 = 0:5) %>%
  # результат прямого расчета для демо-сверки
  mutate(direct_res = (val1 + val2 + val3) * val4)
res <- foreach(it = iter(df, by = "row"), .combine = "c") %do%
  {
    nodeA$in_1 <- it$val1
    nodeA$in_2 <- it$val2
    nodeB$in_2 <- it$val3
    nodeC$in_2 <- it$val4
    shiny:::flushReact()
    nodeC$out()
  }
df$mas_res <- res