EPANET Critical Fixes - History

Purpose: Document critical bugs fixed during Hydrotrek DWD Suite development Period: October 2025 Status: All Fixes Implemented and Verified

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Table of Contents

1. P/Invoke Type Mismatch Fixes
2. Warning vs Error Classification
3. Scenario Export Options Fix
4. Summary

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1. P/Invoke Type Mismatch Fixes

1.1 Problem Summary

Severity: HIGH - Data Corruption Date Discovered: October 20, 2025 Status: ✅ FIXED

Issue: The EPANET wrapper C# P/Invoke declarations had systematic type mismatches where the C API uses double * but C# declarations used ref float. This caused memory corruption because:

• float is 4 bytes (32-bit IEEE 754)
• double is 8 bytes (64-bit IEEE 754)

When C code wrote 8 bytes into a location where C# allocated only 4 bytes, it corrupted adjacent memory.

1.2 Symptoms Observed

Example: Curve Parsing

Input file curve data:

[CURVES]
 1    0.0000      400.0000
 1    1800.0000   300.0000
 1    6000.0000   0.0000

Expected: XValues = {0.0, 1800.0, 6000.0} Actual: XValues = {3.890625, 3.79296875, 0.0} ❌

Impact:

• Wrong curve values in database
• EPANET error 230: "nonincreasing x-values for curve"
• Synchronization failures during scenario runs
• Potential crashes and silent data corruption

1.3 Functions Fixed (10 total)

Function	Issue	Fix	File
EN_getcurvevalue	ref float parameters	ref double	EpanetImport.cs
EN_getcurve	ref float array	ref double	EpanetImport.cs
EN_setcurve	ref float array	ref double	EpanetImport.cs
EN_getdemandmodel	ref float pmin, preq, pexp	ref double	EpanetImport.cs
EN_getbasedemand	ref float baseDemand	ref double	EpanetImport.cs
EN_setpattern	ref float values	ref double	EpanetImport.cs
EN_getcontrol	ref float setting, level	ref double	EpanetImport.cs
EN_getrule	ref float priority	ref double	EpanetImport.cs
EN_getthenaction	ref float setting	ref double	EpanetImport.cs
EN_getelseaction	ref float setting	ref double	EpanetImport.cs

1.4 Files Modified

1. epanetconsolecore/EpanetWrapper/EpanetImport.cs

   • Fixed 10 P/Invoke declarations (ref float → ref double)

2. epanetconsolecore/EpanetWrapper/EpanetWrapper/EpanetWrapper.cs

   • Removed unnecessary float conversions in 3 wrapper methods

3. epanetconsolecore/EpanetWrapper/EpanetWrapper/EpanetWrapperDemand.cs

   • Fixed EN_getdemandmodel signature

4. epanetconsolecore/EpanetWrapper/EpanetWrapper/EpanetWrapperControls.cs

   • Fixed control and rule method signatures

5. epanetconsolecore/NetworkManager/Parsers/OptionsSectionParser.cs

   • Changed caller variables from float to double

6. efcorelibraries/HTModels/Models/EN2Models/DataCurve.cs

   • Added missing case for EN_GENERIC_CURVE in CurveTypeDescription property

1.5 Verification

Before Fix:

• ❌ Curves had garbage values
• ❌ Error 230: "nonincreasing x-values"
• ❌ Synchronization failures
• ❌ Controls/patterns potentially corrupted

After Fix:

• ✅ Curves parse correctly
• ✅ No Error 230
• ✅ Synchronization works
• ✅ All numeric values accurate

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2. Warning vs Error Classification

2.1 Problem Summary

Severity: MEDIUM - Failed Simulations Date Discovered: October 21, 2025 Status: ✅ FIXED

Issue: Error Code 6 (System hydraulically unbalanced) was treated as a fatal error instead of a warning, causing simulations to stop prematurely.

2.2 EPANET GUI Analysis

The EPANET GUI source code reveals the classification rule:

// From simulator.pas
if ErrorCode <= 100 then ErrorCode := epanet2.ENnextH(tstep);
until (tstep = 0) or (ErrorCode > 100) or (SimStatus = ssCancelled);

// Ignore any warning code
if ErrorCode <= 100 then ErrorCode := 0;

Rule:

• Error Codes ≤ 100: Warnings (continue simulation)
• Error Codes > 100: True errors (stop simulation)

2.3 Implementation

File: epanetconsolecore/EpanetWrapper/EpanetWrapper/EpanetWrapper.cs

Named Constant:

// EPANET uses error codes 1-100 for warnings, >100 for true errors
// Reference: EPANET GUI source (USEPA/EPANET/src/simulator/simulator.pas, lines 251, 255, 263, 270)
private const int EPANET_WARNING_THRESHOLD = 100;

Updated Functions:

• EN_runH - Hydraulic solver
• EN_runQ - Quality solver
• EN_nextH - Next hydraulic time step
• EN_nextQ - Next quality time step

Before:

int error = this.EN_runH(ref t);
if (error != 0)
{
    return false;  // Stopped on ANY non-zero code
}

After:

int error = this.EN_runH(ref t);
if (error > EPANET_WARNING_THRESHOLD)
{
    // True errors (>100) - stop simulation
    string errorDescription = GetEpanetErrorDescription(error);
    this.Logger.LogError($"EPANET Error {error} on EN_runH: {errorDescription}");
    return false;
}
else if (error > 0)
{
    // Warnings (1-100) - log but continue
    string warningDescription = GetEpanetErrorDescription(error);
    this.Logger.LogWarning($"EPANET Warning {error} on EN_runH: {warningDescription}");
    // Continue simulation despite warning
}

2.4 Impact

Before Fix:

• ❌ Scenarios 1, 7, 13 failed with "Object reference not set" (masked Error 6)
• ❌ Only Scenario 9 worked
• ❌ Simulations stopped on hydraulic imbalance

After Fix:

• ✅ All scenarios complete successfully
• ✅ Warnings logged but don't stop simulation
• ✅ Results generated even with warnings
• ✅ Clear distinction between warnings and errors

2.5 Common Error Codes

Code	Type	Description	Action
6	⚠️ Warning	System hydraulically unbalanced	Continue
110	❌ Error	Cannot solve network hydraulic equations	Stop
200	❌ Error	Insufficient memory available	Stop
223	❌ Error	Not enough nodes in network	Stop
230	❌ Error	Nonincreasing x-values for curve	Stop

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3. Scenario Export Options Fix

3.1 Problem Summary

Severity: MEDIUM - Incorrect Exports Date Discovered: October 21, 2025 Status: ✅ FIXED

Issue: When exporting INP files for different scenarios, all exported files were identical, even when scenarios had different options (PDA vs DDA).

3.2 Root Cause

The SaveInpFileMode() method in EpanetConsoleCore/Program.cs called SyncAllFromDatabaseAsync() which always synced default options, ignoring scenario-specific options.

Missing:

• Scenario-specific Options (Trials, Accuracy, Tolerance)
• Scenario-specific Demand Model (DDA/PDA with pressure parameters)
• Scenario-specific Controls

3.3 Solution

Created new method: SyncOptionsForScenarioAsync()

private static async Task SyncOptionsForScenarioAsync(
    Scenario scenario, EN2PostgresContext enContext, HTLogger logger)
{
    // Load scenario's options (or fallback to default)
    var options = scenario.Options;
    if (options == null)
    {
        options = await enContext.Options.FirstOrDefaultAsync(o => o.IsDefault)
            ?? await enContext.Options.FirstOrDefaultAsync();
    }

    logger.LogInformation($"Using options: {(scenario.Options != null ? "Scenario-specific" : "Default")} (DemandModel: {options.DemandModel})");

    // Sync using scenario's options
    await networkSyncService.SyncOptionsAsync(options);

    // Sync scenario-specific controls if present
    await networkSyncService.SyncControlsForScenarioAsync(scenario.Id);
}

3.4 Verification

Tested Scenarios:

• ✅ Scenario 7 (PDA): Exported with PDA demand model
• ✅ Scenario 9 (DDA): Exported with DDA demand model
• ✅ Scenarios now have different INP files based on their options

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4. Summary

All Fixes Implemented ✅

Fix	Files Modified	Impact	Status
P/Invoke Type Mismatches	6 files	Data corruption prevented	✅ Complete
Warning Classification	1 file	Simulations no longer fail on warnings	✅ Complete
Scenario Export Options	1 file	Exports now scenario-specific	✅ Complete

Total Impact

Files Modified: 8 files Functions Fixed: 10 P/Invoke declarations + 4 runtime functions Bugs Resolved: 3 critical issues

Result:

• ✅ No more memory corruption
• ✅ Accurate numeric values (curves, controls, patterns)
• ✅ Simulations handle warnings appropriately
• ✅ Scenario exports correctly reflect options
• ✅ System stable and production-ready

Lessons Learned

1. Always match C API types exactly - double * in C = ref double in C#, never ref float
2. Study reference implementations - EPANET GUI source code provided the error classification rule
3. Test with real data - Memory corruption only appeared with actual curve parsing
4. Scenario-specific logic - Always check if scenario has overrides before using defaults

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Related Documentation:

• EPANET API Reference: See epanet2.h
• P/Invoke Guidelines: https://docs.microsoft.com/en-us/dotnet/standard/native-interop/pinvoke
• EPANET GUI Source: USEPA/EPANET repository

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Status: ✅ All Critical Fixes Implemented Last Updated: October 21, 2025 Stability: Production Ready