tune.cpp

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#include <tune_quda.h>
#include <comm_quda.h>
#include <quda.h> // for QUDA_VERSION_STRING
#include <sys/stat.h> // for stat()
#include <fcntl.h>
#include <cfloat> // for FLT_MAX
#include <ctime>
#include <fstream>
#include <typeinfo>
#include <map>

namespace quda {

static const std::string quda_hash = QUDA_HASH; // defined in lib/Makefile
static std::string resource_path;
static std::map<TuneKey, TuneParam> tunecache;
static size_t initial_cache_size = 0;

#define STR_(x) #x
#define STR(x) STR_(x)
static const std::string quda_version = STR(QUDA_VERSION_MAJOR) "." STR(QUDA_VERSION_MINOR) "." STR(QUDA_VERSION_SUBMINOR);
#undef STR
#undef STR_

  static void deserializeTuneCache(std::istream &in)
  {
    std::string line;
    std::stringstream ls;
    TuneKey key;
    TuneParam param;

    while (in.good()) {
      getline(in, line);
      if (!line.length()) continue; // skip blank lines (e.g., at end of file)
      ls.clear();
      ls.str(line);
      ls >> key.volume >> key.name >> key.aux >> param.block.x >> param.block.y >> param.block.z;
      ls >> param.grid.x >> param.grid.y >> param.grid.z >> param.shared_bytes;
      ls.ignore(1); // throw away tab before comment
      getline(ls, param.comment); // assume anything remaining on the line is a comment
      param.comment += "\n"; // our convention is to include the newline, since ctime() likes to do this
      tunecache[key] = param;
    }
  }


  static void serializeTuneCache(std::ostream &out)
  {
    std::map<TuneKey, TuneParam>::iterator entry;

    for (entry = tunecache.begin(); entry != tunecache.end(); entry++) {
      TuneKey key = entry->first;
      TuneParam param = entry->second;

      out << key.volume << "\t" << key.name << "\t" << key.aux << "\t";
      out << param.block.x << "\t" << param.block.y << "\t" << param.block.z << "\t";
      out << param.grid.x << "\t" << param.grid.y << "\t" << param.grid.z << "\t";
      out << param.shared_bytes << "\t" << param.comment; // param.comment ends with a newline
    }
  }


  static void broadcastTuneCache()
  {
#ifdef MULTI_GPU

    std::stringstream serialized;
    size_t size;

    if (comm_rank() == 0) {
      serializeTuneCache(serialized);
      size = serialized.str().length();
    }
    comm_broadcast(&size, sizeof(size_t));

    if (size > 0) {
      if (comm_rank() == 0) {
        comm_broadcast(const_cast<char *>(serialized.str().c_str()), size);
      } else {
        char *serstr = new char[size+1];
        comm_broadcast(serstr, size);
        serstr[size] ='\0'; // null-terminate
        serialized.str(serstr);
        deserializeTuneCache(serialized);
        delete[] serstr;
      }
    }
#endif
  }


  /*
   * Read tunecache from disk.
   */
  void loadTuneCache(QudaVerbosity verbosity)
  {
    char *path;
    struct stat pstat;
    std::string cache_path, line, token;
    std::ifstream cache_file;
    std::stringstream ls;

    path = getenv("QUDA_RESOURCE_PATH");
    if (!path) {
      warningQuda("Environment variable QUDA_RESOURCE_PATH is not set.");
      warningQuda("Caching of tuned parameters will be disabled.");
      return;
    } else if (stat(path, &pstat) || !S_ISDIR(pstat.st_mode)) {
      warningQuda("The path \"%s\" specified by QUDA_RESOURCE_PATH does not exist or is not a directory.", path); 
      warningQuda("Caching of tuned parameters will be disabled.");
      return;
    } else {
      resource_path = path;
    }

#ifdef MULTI_GPU
    if (comm_rank() == 0) {
#endif

      cache_path = resource_path;
      cache_path += "/tunecache.tsv";
      cache_file.open(cache_path.c_str());

      if (cache_file) {

        if (!cache_file.good()) errorQuda("Bad format in %s", cache_path.c_str());
        getline(cache_file, line);
        ls.str(line);
        ls >> token;
        if (token.compare("tunecache")) errorQuda("Bad format in %s", cache_path.c_str());
        ls >> token;
        if (token.compare(quda_version)) errorQuda("Cache file %s does not match current QUDA version", cache_path.c_str());
        ls >> token;
        if (token.compare(quda_hash)) warningQuda("Cache file %s does not match current QUDA build", cache_path.c_str());
      
        if (!cache_file.good()) errorQuda("Bad format in %s", cache_path.c_str());
        getline(cache_file, line); // eat the blank line
      
        if (!cache_file.good()) errorQuda("Bad format in %s", cache_path.c_str());
        getline(cache_file, line); // eat the description line
      
        deserializeTuneCache(cache_file);
        cache_file.close();      
        initial_cache_size = tunecache.size();

        if (verbosity >= QUDA_SUMMARIZE) {
          printfQuda("Loaded %d sets of cached parameters from %s\n", static_cast<int>(initial_cache_size), cache_path.c_str());
        }
      
      } else {
        warningQuda("Cache file not found.  All kernels will be re-tuned (if tuning is enabled).");
      }

#ifdef MULTI_GPU
    }
#endif

    broadcastTuneCache();
  }


  void saveTuneCache(QudaVerbosity verbosity)
  {
    time_t now;
    int lock_handle;
    std::string lock_path, cache_path;
    std::ofstream cache_file;

    if (resource_path.empty()) return;

    //FIXME: We should really check to see if any nodes have tuned a kernel that was not also tuned on node 0, since as things
    //       stand, the corresponding launch parameters would never get cached to disk in this situation.  This will come up if we
    //       ever support different subvolumes per GPU (as might be convenient for lattice volumes that don't divide evenly).

#ifdef MULTI_GPU
    if (comm_rank() == 0) {
#endif

      if (tunecache.size() == initial_cache_size) return;

      // Acquire lock.  Note that this is only robust if the filesystem supports flock() semantics, which is true for
      // NFS on recent versions of linux but not Lustre by default (unless the filesystem was mounted with "-o flock").
      lock_path = resource_path + "/tunecache.lock";
      lock_handle = open(lock_path.c_str(), O_WRONLY | O_CREAT | O_EXCL, 0666);
      if (lock_handle == -1) {
        warningQuda("Unable to lock cache file.  Tuned launch parameters will not be cached to disk.  "
                    "If you are certain that no other instances of QUDA are accessing this filesystem, "
                    "please manually remove %s", lock_path.c_str());
        return;
      }
      char msg[] = "If no instances of applications using QUDA are running,\n"
        "this lock file shouldn't be here and is safe to delete.";
      int stat = write(lock_handle, msg, sizeof(msg)); // check status to avoid compiler warning
      if (stat == -1) warningQuda("Unable to write to lock file for some bizarre reason");

      cache_path = resource_path + "/tunecache.tsv";
      cache_file.open(cache_path.c_str());
    
      if (verbosity >= QUDA_SUMMARIZE) {
        printfQuda("Saving %d sets of cached parameters to %s\n", static_cast<int>(tunecache.size()), cache_path.c_str());
      }
    
      time(&now);
      cache_file << "tunecache\t" << quda_version << "\t" << quda_hash << "\t# Last updated " << ctime(&now) << std::endl;
      cache_file << "volume\tname\taux\tblock.x\tblock.y\tblock.z\tgrid.x\tgrid.y\tgrid.z\tshared_bytes\tcomment" << std::endl;
      serializeTuneCache(cache_file);
      cache_file.close();

      // Release lock.
      close(lock_handle);
      remove(lock_path.c_str());

      initial_cache_size = tunecache.size();

#ifdef MULTI_GPU
    }
#endif
  }

  TuneParam tuneLaunch(Tunable &tunable, QudaTune enabled, QudaVerbosity verbosity)
  {
    // We must switch off the global sum when tuning in case of process divergence
    bool reduceState = globalReduce;
    globalReduce = false;

    static bool tuning = false; // tuning in progress?
    static const Tunable *active_tunable; // for error checking
    static TuneParam param;

    TuneParam best_param;
    cudaError_t error;
    cudaEvent_t start, end;
    float elapsed_time, best_time;
    time_t now;

    const TuneKey key = tunable.tuneKey();

    if (enabled == QUDA_TUNE_NO) {
      tunable.defaultTuneParam(param);
      tunable.checkLaunchParam(param);
    } else if (tunecache.count(key)) {
      param = tunecache[key];
      tunable.checkLaunchParam(param);
    } else if (!tuning) {

      tuning = true;
      active_tunable = &tunable;
      best_time = FLT_MAX;

      if (verbosity >= QUDA_DEBUG_VERBOSE) printfQuda("PreTune %s\n", key.name.c_str());
      tunable.preTune();

      cudaEventCreate(&start);
      cudaEventCreate(&end);

      if (verbosity >= QUDA_DEBUG_VERBOSE) {
        printfQuda("Tuning %s with %s at vol=%s\n", key.name.c_str(), key.aux.c_str(), key.volume.c_str());
      }

      tunable.initTuneParam(param);
      while (tuning) {
        cudaDeviceSynchronize();
        cudaGetLastError(); // clear error counter
        tunable.checkLaunchParam(param);
        cudaEventRecord(start, 0);
        for (int i=0; i<tunable.tuningIter(); i++) {
          tunable.apply(0);  // calls tuneLaunch() again, which simply returns the currently active param
        }
        cudaEventRecord(end, 0);
        cudaEventSynchronize(end);
        cudaEventElapsedTime(&elapsed_time, start, end);
        cudaDeviceSynchronize();
        error = cudaGetLastError();
        elapsed_time /= (1e3 * tunable.tuningIter());
        if ((elapsed_time < best_time) && (error == cudaSuccess)) {
          best_time = elapsed_time;
          best_param = param;
        }
        if ((verbosity >= QUDA_DEBUG_VERBOSE)) {
          if (error == cudaSuccess)
            printfQuda("    %s gives %s\n", tunable.paramString(param).c_str(), 
                       tunable.perfString(elapsed_time).c_str());
          else 
            printfQuda("    %s gives %s\n", tunable.paramString(param).c_str(), cudaGetErrorString(error));
        }
        tuning = tunable.advanceTuneParam(param);
      }

      if (best_time == FLT_MAX) {
        errorQuda("Auto-tuning failed for %s with %s at vol=%s", key.name.c_str(), key.aux.c_str(), key.volume.c_str());
      }
      if (verbosity >= QUDA_VERBOSE) {
        printfQuda("Tuned %s giving %s for %s with %s\n", tunable.paramString(best_param).c_str(),
                   tunable.perfString(best_time).c_str(), key.name.c_str(), key.aux.c_str());
      }
      time(&now);
      best_param.comment = "# " + tunable.perfString(best_time) + ", tuned ";
      best_param.comment += ctime(&now); // includes a newline

      cudaEventDestroy(start);
      cudaEventDestroy(end);

      if (verbosity >= QUDA_DEBUG_VERBOSE) printfQuda("PostTune %s\n", key.name.c_str());
      tunable.postTune();
      param = best_param;
      tunecache[key] = best_param;

    } else if (&tunable != active_tunable) {
      errorQuda("Unexpected call to tuneLaunch() in %s::apply()", typeid(tunable).name());
    }

    // restore the original reduction state
    globalReduce = reduceState;

    return param;
  }

} // namespace quda