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-rw-r--r--src/core/lib/support/histogram.cc227
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diff --git a/src/core/lib/support/histogram.cc b/src/core/lib/support/histogram.cc
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--- a/src/core/lib/support/histogram.cc
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-/*
- *
- * Copyright 2015 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-#include <grpc/support/histogram.h>
-
-#include <math.h>
-#include <stddef.h>
-#include <string.h>
-
-#include <grpc/support/alloc.h>
-#include <grpc/support/log.h>
-#include <grpc/support/port_platform.h>
-#include <grpc/support/useful.h>
-
-/* Histograms are stored with exponentially increasing bucket sizes.
- The first bucket is [0, m) where m = 1 + resolution
- Bucket n (n>=1) contains [m**n, m**(n+1))
- There are sufficient buckets to reach max_bucket_start */
-
-struct gpr_histogram {
- /* Sum of all values seen so far */
- double sum;
- /* Sum of squares of all values seen so far */
- double sum_of_squares;
- /* number of values seen so far */
- double count;
- /* m in the description */
- double multiplier;
- double one_on_log_multiplier;
- /* minimum value seen */
- double min_seen;
- /* maximum value seen */
- double max_seen;
- /* maximum representable value */
- double max_possible;
- /* number of buckets */
- size_t num_buckets;
- /* the buckets themselves */
- uint32_t* buckets;
-};
-
-/* determine a bucket index given a value - does no bounds checking */
-static size_t bucket_for_unchecked(gpr_histogram* h, double x) {
- return (size_t)(log(x) * h->one_on_log_multiplier);
-}
-
-/* bounds checked version of the above */
-static size_t bucket_for(gpr_histogram* h, double x) {
- size_t bucket = bucket_for_unchecked(h, GPR_CLAMP(x, 1.0, h->max_possible));
- GPR_ASSERT(bucket < h->num_buckets);
- return bucket;
-}
-
-/* at what value does a bucket start? */
-static double bucket_start(gpr_histogram* h, double x) {
- return pow(h->multiplier, x);
-}
-
-gpr_histogram* gpr_histogram_create(double resolution,
- double max_bucket_start) {
- gpr_histogram* h = (gpr_histogram*)gpr_malloc(sizeof(gpr_histogram));
- GPR_ASSERT(resolution > 0.0);
- GPR_ASSERT(max_bucket_start > resolution);
- h->sum = 0.0;
- h->sum_of_squares = 0.0;
- h->multiplier = 1.0 + resolution;
- h->one_on_log_multiplier = 1.0 / log(1.0 + resolution);
- h->max_possible = max_bucket_start;
- h->count = 0.0;
- h->min_seen = max_bucket_start;
- h->max_seen = 0.0;
- h->num_buckets = bucket_for_unchecked(h, max_bucket_start) + 1;
- GPR_ASSERT(h->num_buckets > 1);
- GPR_ASSERT(h->num_buckets < 100000000);
- h->buckets = (uint32_t*)gpr_zalloc(sizeof(uint32_t) * h->num_buckets);
- return h;
-}
-
-void gpr_histogram_destroy(gpr_histogram* h) {
- gpr_free(h->buckets);
- gpr_free(h);
-}
-
-void gpr_histogram_add(gpr_histogram* h, double x) {
- h->sum += x;
- h->sum_of_squares += x * x;
- h->count++;
- if (x < h->min_seen) {
- h->min_seen = x;
- }
- if (x > h->max_seen) {
- h->max_seen = x;
- }
- h->buckets[bucket_for(h, x)]++;
-}
-
-int gpr_histogram_merge(gpr_histogram* dst, const gpr_histogram* src) {
- if ((dst->num_buckets != src->num_buckets) ||
- (dst->multiplier != src->multiplier)) {
- /* Fail because these histograms don't match */
- return 0;
- }
- gpr_histogram_merge_contents(dst, src->buckets, src->num_buckets,
- src->min_seen, src->max_seen, src->sum,
- src->sum_of_squares, src->count);
- return 1;
-}
-
-void gpr_histogram_merge_contents(gpr_histogram* dst, const uint32_t* data,
- size_t data_count, double min_seen,
- double max_seen, double sum,
- double sum_of_squares, double count) {
- size_t i;
- GPR_ASSERT(dst->num_buckets == data_count);
- dst->sum += sum;
- dst->sum_of_squares += sum_of_squares;
- dst->count += count;
- if (min_seen < dst->min_seen) {
- dst->min_seen = min_seen;
- }
- if (max_seen > dst->max_seen) {
- dst->max_seen = max_seen;
- }
- for (i = 0; i < dst->num_buckets; i++) {
- dst->buckets[i] += data[i];
- }
-}
-
-static double threshold_for_count_below(gpr_histogram* h, double count_below) {
- double count_so_far;
- double lower_bound;
- double upper_bound;
- size_t lower_idx;
- size_t upper_idx;
-
- if (h->count == 0) {
- return 0.0;
- }
-
- if (count_below <= 0) {
- return h->min_seen;
- }
- if (count_below >= h->count) {
- return h->max_seen;
- }
-
- /* find the lowest bucket that gets us above count_below */
- count_so_far = 0.0;
- for (lower_idx = 0; lower_idx < h->num_buckets; lower_idx++) {
- count_so_far += h->buckets[lower_idx];
- if (count_so_far >= count_below) {
- break;
- }
- }
- if (count_so_far == count_below) {
- /* this bucket hits the threshold exactly... we should be midway through
- any run of zero values following the bucket */
- for (upper_idx = lower_idx + 1; upper_idx < h->num_buckets; upper_idx++) {
- if (h->buckets[upper_idx]) {
- break;
- }
- }
- return (bucket_start(h, (double)lower_idx) +
- bucket_start(h, (double)upper_idx)) /
- 2.0;
- } else {
- /* treat values as uniform throughout the bucket, and find where this value
- should lie */
- lower_bound = bucket_start(h, (double)lower_idx);
- upper_bound = bucket_start(h, (double)(lower_idx + 1));
- return GPR_CLAMP(upper_bound - (upper_bound - lower_bound) *
- (count_so_far - count_below) /
- h->buckets[lower_idx],
- h->min_seen, h->max_seen);
- }
-}
-
-double gpr_histogram_percentile(gpr_histogram* h, double percentile) {
- return threshold_for_count_below(h, h->count * percentile / 100.0);
-}
-
-double gpr_histogram_mean(gpr_histogram* h) {
- GPR_ASSERT(h->count != 0);
- return h->sum / h->count;
-}
-
-double gpr_histogram_stddev(gpr_histogram* h) {
- return sqrt(gpr_histogram_variance(h));
-}
-
-double gpr_histogram_variance(gpr_histogram* h) {
- if (h->count == 0) return 0.0;
- return (h->sum_of_squares * h->count - h->sum * h->sum) /
- (h->count * h->count);
-}
-
-double gpr_histogram_maximum(gpr_histogram* h) { return h->max_seen; }
-
-double gpr_histogram_minimum(gpr_histogram* h) { return h->min_seen; }
-
-double gpr_histogram_count(gpr_histogram* h) { return h->count; }
-
-double gpr_histogram_sum(gpr_histogram* h) { return h->sum; }
-
-double gpr_histogram_sum_of_squares(gpr_histogram* h) {
- return h->sum_of_squares;
-}
-
-const uint32_t* gpr_histogram_get_contents(gpr_histogram* h, size_t* size) {
- *size = h->num_buckets;
- return h->buckets;
-}