13_map_reduce.c

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/* -*- C -*-
 * Serene programming language
 * Copyright (C) 2019-2026 Sameer Rahmani <[email protected]>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 
// Example 13 -- A naive and imperative map/reduce, ish
 
#include <stdint.h>
#include <stdio.h>
 
#include <serene/rt/trace.h>
#include <serene/runtime.h>
 
#include "serene/utils.h"
 
#define NUMBER_OF_ELEMENTS 1000
 
typedef uint64_t (*mapper_f)(uint64_t v);
 
typedef struct mapper_args_t {
  uint64_t val;
  mapper_f f;
} mapper_args_t;
 
static uint64_t add_1(uint64_t v) { return v + 10; }
 
static srn_fiber_result_t mapper_fiber(srn_context_t *ctx, void *arg) {
  (void)ctx;
  auto mapper_args = (mapper_args_t *)arg;
 
  uint64_t val = mapper_args->f(mapper_args->val);
  return (void *)(uintptr_t)val;
}
 
static int main_13(srn_context_t *ctx, int argc, char **argv) {
  UNUSED(argc);
  UNUSED(argv);
 
  srn_fiber_t *fibers[NUMBER_OF_ELEMENTS];
 
  uint64_t xs[NUMBER_OF_ELEMENTS] = {0};
 
  for (int i = 0; i < NUMBER_OF_ELEMENTS; i++) {
    // Fan out, one mapper per element. SRN_FIBER_SPAWN_COPY copies the argument
    // into the context, so each fiber owns its own copy and the loop-local
    // `args` can die at the end of the iteration.
    mapper_args_t args = {
      .val = i,
      .f   = &add_1,
    };
    fibers[i] = SRN_FIBER_SPAWN_COPY(ctx, mapper_fiber, args);
  }
 
  // Fan in, join each mapper and read the value it returned.
  for (int i = 0; i < NUMBER_OF_ELEMENTS; i++) {
    xs[i] = (uint64_t)(uintptr_t)srn_fiber_wait_for(fibers[i]);
  }
 
  for (int i = 0; i < NUMBER_OF_ELEMENTS; i++) {
    printf(">> %lu\n", xs[i]);
  };
 
  return 0;
}
 
SERENE_MAIN(main_13)