scirs2-integrate 0.5.1

Numerical integration module for SciRS2 (scirs2-integrate)
Documentation
//! Performance monitoring implementation
//!
//! This module contains the implementation for performance monitoring,
//! metrics collection, and system resource tracking.

use super::types::*;
use crate::common::IntegrateFloat;
use crate::error::{IntegrateError, IntegrateResult};
use std::time::{Duration, Instant};

impl PerformanceMonitoringEngine {
    /// Create a new performance monitoring engine
    pub fn new() -> Self {
        Self {
            metrics_collector: MetricsCollector::default(),
            performance_history: PerformanceHistory::default(),
            system_monitor: SystemResourceMonitor::default(),
            network_monitor: NetworkPerformanceMonitor::default(),
        }
    }

    /// Start continuous performance monitoring
    pub fn start_monitoring(&mut self) -> IntegrateResult<()> {
        // Implementation for starting monitoring would go here
        Ok(())
    }

    /// Stop performance monitoring
    pub fn stop_monitoring(&mut self) -> IntegrateResult<()> {
        // Implementation for stopping monitoring would go here
        Ok(())
    }

    /// Collect current performance metrics.
    ///
    /// This lightweight monitor reports only the quantities it can genuinely
    /// observe from the host:
    ///
    /// * `timestamp` — the real wall-clock instant of the sample.
    /// * `step_time` — the elapsed time since the previous sample (the
    ///   sampling cadence). On the very first sample this is zero.
    /// * `memory_usage` — the process resident set size (RSS) read from the
    ///   operating system. Returns `0` on platforms where it cannot be read.
    ///
    /// The remaining fields (CPU/GPU utilisation, cache-hit rate, network
    /// bandwidth, solver error/convergence) require hardware performance
    /// counters or solver-level instrumentation that this monitor does not
    /// have. Rather than fabricating plausible-looking values, they are
    /// reported as `0.0` to signal "not measured". Callers that need those
    /// quantities must feed them in through a dedicated instrumentation path.
    pub fn collect_metrics(&mut self) -> IntegrateResult<PerformanceMetrics> {
        let timestamp = Instant::now();

        // Real sampling interval: time elapsed since the previous sample.
        let step_time = self
            .performance_history
            .metrics_history
            .back()
            .map(|prev| timestamp.saturating_duration_since(prev.timestamp))
            .unwrap_or_else(|| Duration::from_secs(0));

        // Real process resident-set-size in bytes (0 if unavailable).
        let memory_usage = Self::process_resident_memory_bytes();

        // Throughput is samples-per-second of the monitor itself when we have
        // a positive interval; otherwise it is unknown (0.0).
        let throughput = if step_time > Duration::from_secs(0) {
            1.0 / step_time.as_secs_f64()
        } else {
            0.0
        };

        let metrics = PerformanceMetrics::new(
            timestamp,
            step_time,
            throughput,
            memory_usage,
            0.0, // cpu_utilization: requires per-core counters (not measured)
            0.0, // gpu_utilization: requires a GPU runtime (not measured)
            0.0, // cache_hit_rate: requires hardware counters (not measured)
            0.0, // network_bandwidth: requires NIC counters (not measured)
            0.0, // error_accuracy: requires solver instrumentation (not measured)
            0.0, // convergence_rate: requires solver instrumentation (not measured)
        );

        self.performance_history.add_metrics(metrics.clone());
        Ok(metrics)
    }

    /// Read the current process resident set size (RSS) in bytes.
    ///
    /// Returns `0` when the value cannot be determined on the current
    /// platform (e.g. `/proc` is unavailable).
    fn process_resident_memory_bytes() -> usize {
        #[cfg(target_os = "linux")]
        {
            // `/proc/self/status` exposes `VmRSS` directly in kibibytes, which
            // avoids any dependency on the system page size.
            if let Ok(contents) = std::fs::read_to_string("/proc/self/status") {
                for line in contents.lines() {
                    if let Some(rest) = line.strip_prefix("VmRSS:") {
                        if let Some(kb_str) = rest.split_whitespace().next() {
                            if let Ok(kb) = kb_str.parse::<usize>() {
                                return kb.saturating_mul(1024);
                            }
                        }
                    }
                }
            }
            0
        }
        #[cfg(not(target_os = "linux"))]
        {
            0
        }
    }

    /// Get performance analysis from collected metrics
    pub fn get_performance_analysis(&self) -> IntegrateResult<PerformanceAnalysis> {
        if self.performance_history.metrics_history.is_empty() {
            return Ok(PerformanceAnalysis {
                average_throughput: 0.0,
                average_cpu_utilization: 0.0,
                average_memory_usage: 0,
                performance_trend: PerformanceTrend::Stable,
                bottlenecks: Vec::new(),
            });
        }

        let metrics = &self.performance_history.metrics_history;
        let count = metrics.len() as f64;

        let avg_throughput = metrics.iter().map(|m| m.throughput).sum::<f64>() / count;
        let avg_cpu = metrics.iter().map(|m| m.cpu_utilization).sum::<f64>() / count;
        let avg_memory = metrics.iter().map(|m| m.memory_usage).sum::<usize>() / metrics.len();

        // Simple trend analysis
        let trend = if metrics.len() > 1 {
            let recent_avg = metrics
                .iter()
                .rev()
                .take(5)
                .map(|m| m.throughput)
                .sum::<f64>()
                / 5.0_f64.min(metrics.len() as f64);
            let older_avg = metrics.iter().take(5).map(|m| m.throughput).sum::<f64>()
                / 5.0_f64.min(metrics.len() as f64);

            if recent_avg > older_avg * 1.05 {
                PerformanceTrend::Improving
            } else if recent_avg < older_avg * 0.95 {
                PerformanceTrend::Degrading
            } else {
                PerformanceTrend::Stable
            }
        } else {
            PerformanceTrend::Stable
        };

        // Simple bottleneck detection
        let mut bottlenecks = Vec::new();
        if avg_cpu > 80.0 {
            bottlenecks.push(PerformanceBottleneck::CPU);
        }
        if avg_memory > 1024 * 1024 * 1024 {
            bottlenecks.push(PerformanceBottleneck::Memory);
        }

        Ok(PerformanceAnalysis {
            average_throughput: avg_throughput,
            average_cpu_utilization: avg_cpu,
            average_memory_usage: avg_memory,
            performance_trend: trend,
            bottlenecks,
        })
    }
}

impl PerformanceHistory {
    /// Add new metrics to history
    pub fn add_metrics(&mut self, metrics: PerformanceMetrics) {
        self.metrics_history.push_back(metrics);

        // Keep history size under limit
        if self.metrics_history.len() > self.max_history_size {
            self.metrics_history.pop_front();
        }
    }

    /// Clear all history
    pub fn clear(&mut self) {
        self.metrics_history.clear();
        self.aggregated_stats.clear();
    }
}