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//===--- Histogram.h - Simple histogram for statistics ----------*- C++ -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2021 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/ArrayRef.h"
#ifndef SWIFT_HISTOGRAM_H
#define SWIFT_HISTOGRAM_H
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <vector>
namespace swift {
namespace rewriting {
/// A simple histogram that supports two operations: recording an element, and
/// printing a graphical representation.
///
/// Used by the rewrite system to record various statistics, which are dumped
/// when the -analyze-requirement-machine frontend flag is used.
class Histogram {
unsigned Size;
unsigned Start;
std::vector<unsigned> Buckets;
unsigned OverflowBucket;
unsigned MaxValue = 0;
const unsigned MaxWidth = 40;
/// This is not really the base-10 logarithm, but rather the number of digits
/// in \p x when printed in base 10.
///
/// So log10(0) == 1, log10(1) == 1, log10(10) == 2, etc.
static unsigned log10(unsigned x) {
if (x == 0)
return 1;
unsigned result = 0;
while (x != 0) {
result += 1;
x /= 10;
}
return result;
}
public:
/// Creates a histogram with \p size buckets, where the numbering begins at
/// \p start.
Histogram(unsigned size, unsigned start = 0)
: Size(size),
Start(start),
Buckets(size, 0),
OverflowBucket(0) {
}
/// Adds an entry to the histogram. Asserts if the \p value is smaller than
/// Start. The value is allowed to be greater than or equal to Start + Size,
/// in which case it's counted in the OverflowBucket.
void add(unsigned value) {
assert(value >= Start);
value -= Start;
if (value >= Size)
++OverflowBucket;
else
++Buckets[value];
if (value > MaxValue)
MaxValue = value;
}
/// Print a nice-looking graphical representation of the histogram.
void dump(llvm::raw_ostream &out, const StringRef labels[] = {}) {
unsigned sumValues = 0;
unsigned maxValue = 0;
for (unsigned i = 0; i < Size; ++i) {
sumValues += Buckets[i];
maxValue = std::max(maxValue, Buckets[i]);
}
sumValues += OverflowBucket;
maxValue = std::max(maxValue, OverflowBucket);
size_t maxLabelWidth = 3 + log10(Size + Start);
if (labels != nullptr) {
for (unsigned i = 0; i < Size; ++i)
maxLabelWidth = std::max(labels[i].size(), maxLabelWidth);
}
out << std::string(maxLabelWidth, ' ') << " |";
out << std::string(std::min(MaxWidth, maxValue), ' ');
out << maxValue << "\n";
out << std::string(maxLabelWidth, ' ') << " |";
out << std::string(std::min(MaxWidth, maxValue), ' ');
out << "*\n";
out << std::string(maxLabelWidth, '-') << "-+-";
out << std::string(std::min(MaxWidth, maxValue), '-') << "\n";
auto scaledValue = [&](unsigned value) {
if (maxValue > MaxWidth) {
if (value != 0) {
// If the value is non-zero, print at least one '#'.
return std::max(1U, (value * MaxWidth) / maxValue);
}
}
return value;
};
for (unsigned i = 0; i < Size; ++i) {
if (labels) {
out << std::string(maxLabelWidth - labels[i].size(), ' ');
out << labels[i];
} else {
unsigned key = i + Start;
out << std::string(maxLabelWidth - log10(key), ' ');
out << key;
}
out << " | ";
unsigned value = scaledValue(Buckets[i]);
out << std::string(value, '#') << "\n";
}
if (OverflowBucket > 0) {
out << ">= " << (Size + Start) << " | ";
unsigned value = scaledValue(OverflowBucket);
out << std::string(value, '#') << "\n";
}
out << std::string(maxLabelWidth, '-') << "-+-";
out << std::string(std::min(MaxWidth, maxValue), '-') << "\n";
out << std::string(maxLabelWidth, ' ') << " | ";
out << "Total: " << sumValues << "\n";
out << std::string(maxLabelWidth, ' ') << " | ";
out << "Max: " << MaxValue << "\n";
}
};
} // end namespace rewriting
} // end namespace swift
#endif
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