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merge_external.c
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merge_external.c
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#include "merge.h"
//manager fields should be already initialized in the caller
int merge_runs (MergeManager * merger){
int result; //stores SUCCESS/FAILURE returned at the end
OUTPUT_ELEMENT_T output_result;
int f_id ;
//1. go in the loop through all input files and fill-in initial buffers
if (init_merge (merger)!=SUCCESS)
return FAILURE;
output_result.file_number = -1;
merger->lastTransferred.file_number = -1;
while (merger->currentHeapSize > 0) { //heap is not empty
HEAP_ELEMENT_T smallest;
INPUT_ELEMENT_T next; //here next is of input_type
if(get_top_heap_element (merger, &smallest)!=SUCCESS)
return FAILURE;
result = get_next_input_element (merger, smallest.file_number, &next);
if (result==FAILURE)
return FAILURE;
if(result==SUCCESS) {//next element exists
if (merger->lastTransferred.file_number == -1 )
base_current_rank = smallest.currentRank;
if(insert_into_heap (merger,smallest.file_number, &next)!=SUCCESS)
return FAILURE;
}
if(heap_to_output ( &(merger->lastTransferred), &smallest, &output_result)!=SUCCESS)
return FAILURE;
if (valid_output(&output_result)) { //app-specific
f_id = output_result.file_number;
merger->outputBuffers[f_id][merger->currentOutputBufferPositions[f_id]]=output_result;
merger->currentOutputBufferPositions[f_id]++;
//staying on the last slot of the output buffer - next will cause overflow
if(merger->currentOutputBufferPositions[f_id] == merger-> outputBufferCapacity ) {
if(flush_output_buffers(merger, f_id)!=SUCCESS)
return FAILURE;
merger->currentOutputBufferPositions[f_id]=0;
}
}
if (merger->currentHeapSize == 0) { //last heap element
heap_to_output_last_element (&(merger->lastTransferred), &smallest, &output_result);
f_id = output_result.file_number;
if(merger->currentOutputBufferPositions[f_id] == merger-> outputBufferCapacity ) {
if(flush_output_buffers(merger, f_id)!=SUCCESS)
return FAILURE;
merger->currentOutputBufferPositions[f_id]=0;
}
merger->outputBuffers[f_id][merger->currentOutputBufferPositions[f_id] ]=output_result;
merger->currentOutputBufferPositions[f_id] ++;
}
merger->lastTransferred = smallest;
}
//flush what remains in output buffer
for (f_id=0; f_id< merger->total_files; f_id++) {
if(merger->currentOutputBufferPositions[f_id] > 0) {
if(flush_output_buffers(merger, f_id)!=SUCCESS)
return FAILURE;
}
}
if (DEBUG) printf("Merge complete.\n");
clean_up(merger);
return SUCCESS;
}
int init_merge (MergeManager * merger) {
int i;
INPUT_ELEMENT_T first = {0};
for(i=0;i<merger->heapCapacity;i++) {
if (refill_buffer(merger,i) == FAILURE){
fprintf(stderr, "Failed to fill initial buffer %d\n",i);
return FAILURE;
}
}
for (i=0;i<merger->heapCapacity;i++) {
//get element from each buffer
if(get_next_input_element (merger,i, &first)==FAILURE) //at least 1 element should exist
return FAILURE;
//insert it into heap
if(insert_into_heap (merger, i, &first)!=SUCCESS)
return FAILURE;
}
return SUCCESS;
}
int get_top_heap_element (MergeManager * merger, HEAP_ELEMENT_T * result){
HEAP_ELEMENT_T item;
int child, parent;
if(merger->currentHeapSize == 0){
printf( "UNEXPECTED ERROR: popping top element from an empty heap\n");
return FAILURE;
}
*result=merger->heap[0]; //to be returned
//now we need to reorganize heap - keep the smallest on top
item = merger->heap [--merger->currentHeapSize]; // to be reinserted
parent =0;
while ((child = (2 * parent) + 1) < merger->currentHeapSize) {
// if there are two children, compare them
if (child + 1 < merger->currentHeapSize &&
(compare_heap_elements(&(merger->heap[child]),&(merger->heap[child + 1]))>0))
++child;
// compare item with the larger
if (compare_heap_elements(&item, &(merger->heap[child]))>0) {
merger->heap[parent] = merger->heap[child];
parent = child;
}
else
break;
}
merger->heap[parent] = item;
return SUCCESS;
}
int insert_into_heap (MergeManager * merger, int file_number, INPUT_ELEMENT_T *input){
HEAP_ELEMENT_T newHeapElement;
int child, parent;
if (input_to_heap (input, file_number, &newHeapElement) != SUCCESS)
return FAILURE;
if (merger->currentHeapSize == merger->heapCapacity) {
printf( "Unexpected ERROR: heap is full\n");
return FAILURE;
}
child = merger->currentHeapSize++; /* the next available slot in the heap */
while (child > 0) {
parent = (child - 1) / 2;
if (compare_heap_elements(&(merger->heap[parent]),&newHeapElement)>0) {
merger->heap[child] = merger->heap[parent];
child = parent;
}
else
break;
}
merger->heap[child]= newHeapElement;
return SUCCESS;
}
int get_next_input_element (MergeManager * merger, int file_number,
INPUT_ELEMENT_T *result){
if(merger->currentInputBufferPositions[file_number] == -1) //run is complete
return EMPTY; //empty
//there are still elements in the buffer
if(merger->currentInputBufferPositions[file_number] < merger->currentInputBufferlengths[file_number])
*result= merger->inputBuffers[file_number][merger->currentInputBufferPositions[file_number]++];
else {
int refillResult = refill_buffer (merger, file_number);
if(refillResult==SUCCESS)
return get_next_input_element (merger, file_number, result);
else
return refillResult;
}
return SUCCESS; //success
}
int input_to_heap (INPUT_ELEMENT_T *input, int file_number, HEAP_ELEMENT_T *result){
result->currentRank = input->currentRank;
result->nextRank = input->nextRank;
result->count = input->count;
result->file_number = file_number;
return SUCCESS;
}
void clean_up(MergeManager * merger)
{
int i;
for (i=0; i<merger->total_files;i++)
free(merger->inputBuffers [i]);
free(merger->inputBuffers);
free(merger->currentInputFilePositions);
free(merger->currentInputBufferPositions);
free(merger->currentInputBufferlengths);
for (i=0; i<merger->total_files;i++)
free(merger->outputBuffers [i]);
free(merger->outputBuffers);
free(merger->currentOutputBufferPositions);
free(merger->heap);
free(merger->inputFileNumbers);
}
int refill_buffer (MergeManager * merger, int file_number) {
char currentInputFileName[MAX_PATH_LENGTH];
int result;
if(merger->currentInputFilePositions[file_number] == -1) {
merger->currentInputBufferPositions[file_number] = -1; //signifies no more elements
return EMPTY; //run is complete - no more elements in the input file
}
sprintf(currentInputFileName, "%s/run_%d_%d" , merger->output_dir, merger->inputFileNumbers[file_number].file_id,
merger->inputFileNumbers[file_number].interval_id);
OpenBinaryFileRead (&(merger->inputFP), currentInputFileName);
result = fseek ( merger->inputFP , merger->currentInputFilePositions[file_number]*sizeof (RunRecord) , SEEK_SET );
if (result!=SUCCESS) {
printf ("fseek failed on file %s trying to move to position %ld\n", currentInputFileName,
merger->currentInputFilePositions[file_number]*sizeof (RunRecord) );
return FAILURE;
}
if ((result = fread (merger->inputBuffers[file_number], sizeof (RunRecord), merger->inputBufferCapacity, merger->inputFP)) > 0) {
merger->currentInputBufferPositions[file_number] = 0;
merger->currentInputBufferlengths [file_number] = result;
merger->currentInputFilePositions [file_number] += result;
fclose(merger->inputFP);
merger->inputFP = NULL;
if (result < merger->inputBufferCapacity) //no more reads
merger->currentInputFilePositions [file_number] = -1;
return SUCCESS;
}
//no more elements - we read exactly until the end of the file in the previous upload
merger->currentInputFilePositions [file_number] = -1;
merger->currentInputBufferPositions[file_number] = -1;
fclose(merger->inputFP);
merger->inputFP = NULL;
return EMPTY;
}