Fix potential out-of-bounds memory in IdealClusterBuilder

[tvami]

I am updating ldmx-sw, here are the details.

Replace initializer-list vector assignments (= {val}) with push_back to avoid a compiler/ASAN warning about potential out-of-bounds memmove; this works because std::map::operator[] default-constructs an empty vector when the key doesn't exist, so push_back on it is safe without an explicit count check.

What are the issues that this addresses?

Resolves #1707

Check List

• I successfully compiled ldmx-sw with my developments.
• I read, understood and follow the coding rules.

• I ran my developments and the following shows that they are successful.

[tvami]

This is ready for review, but the gold creation is in progress so I kept it draft until that finishes.

[github-actions]

Validation Results

Some validation samples failed! ❌

Sample	Status
deep_ecal_gun	✅ PASS
eat_signal	✅ PASS
ecal_pn	✅ PASS
hcal	✅ PASS
inclusive	✅ PASS
it_pileup	✅ PASS
kaon_enhanced	✅ PASS
reduced_ldmx	✅ PASS
signal	✅ PASS
signal_target_al	✅ PASS
target_genie	✅ PASS
target_pn_lyso	✅ PASS
target_ti_en	✅ PASS
wab_lhe	✅ PASS
cascade_history	❌ FAIL (82 histograms failed KS test) (artifact)

cascade_history:

• 82 plots failed the KS test against gold.
• Text Differences Between Logs (69763 lines differ)
• Log character count differs by 2%: gold=4450203, new=4355143
• Timing for cascade_history: gold=5968s, new=6244s
• Timing within 4% of gold (tolerance 10%)

deep_ecal_gun:

• Text Differences Between Logs (20 lines differ)
• Timing anomaly for deep_ecal_gun: new=3197s vs gold=4091s (-21%, tolerance 10%)
• Timing for deep_ecal_gun: gold=4091s, new=3197s

eat_signal:

• Timing for eat_signal: gold=1602s, new=1548s
• Timing within 3% of gold (tolerance 10%)

ecal_pn:

• Text Differences Between Logs (44 lines differ)
• Timing for ecal_pn: gold=6232s, new=6511s
• Timing within 4% of gold (tolerance 10%)

hcal:

• Text Differences Between Logs (2 lines differ)
• Timing for hcal: gold=829s, new=764s
• Timing within 7% of gold (tolerance 10%)

inclusive:

• Text Differences Between Logs (20 lines differ)
• Timing for inclusive: gold=6805s, new=6784s
• Timing within 0% of gold (tolerance 10%)

it_pileup:

• Text Differences Between Logs (44 lines differ)
• Timing for it_pileup: gold=577s, new=567s
• Timing within 1% of gold (tolerance 10%)

kaon_enhanced:

• Text Differences Between Logs (22 lines differ)
• Timing for kaon_enhanced: gold=3122s, new=3090s
• Timing within 1% of gold (tolerance 10%)

reduced_ldmx:

• Text Differences Between Logs (22 lines differ)
• Timing for reduced_ldmx: gold=211s, new=213s
• Timing within 0% of gold (tolerance 10%)

signal:

• Text Differences Between Logs (38 lines differ)
• Timing for signal: gold=1184s, new=1203s
• Timing within 1% of gold (tolerance 10%)

signal_target_al:

• Text Differences Between Logs (28 lines differ)
• Timing for signal_target_al: gold=1047s, new=1078s
• Timing within 2% of gold (tolerance 10%)

target_genie:

• Text Differences Between Logs (4480 lines differ)
• Timing for target_genie: gold=6488s, new=6545s
• Timing within 0% of gold (tolerance 10%)

target_pn_lyso:

• Text Differences Between Logs (28 lines differ)
• Timing for target_pn_lyso: gold=6455s, new=6380s
• Timing within 1% of gold (tolerance 10%)

target_ti_en:

• Text Differences Between Logs (38 lines differ)
• Timing for target_ti_en: gold=3226s, new=3126s
• Timing within 3% of gold (tolerance 10%)

wab_lhe:

• Text Differences Between Logs (30 lines differ)
• Timing for wab_lhe: gold=6770s, new=6503s
• Timing within 3% of gold (tolerance 10%)

[tvami]

/run-validation

[github-actions]

The validation workflow is running here: https://github.com/LDMX-Software/ldmx-sw/actions/runs/27662256723.

[tvami]

cascade_history does not run the IdealClusterBuilder... it actually just runs the PN, which has been stable so far. Let's see the next test

[github-actions]

Validation Results

Some validation samples failed! ❌

Sample	Status
cascade_history	✅ PASS
deep_ecal_gun	✅ PASS
eat_signal	✅ PASS
ecal_pn	✅ PASS
hcal	✅ PASS
inclusive	✅ PASS
it_pileup	✅ PASS
kaon_enhanced	✅ PASS
reduced_ldmx	✅ PASS
signal	✅ PASS
signal_target_al	✅ PASS
target_pn_lyso	✅ PASS
target_ti_en	✅ PASS
wab_lhe	✅ PASS
target_genie	❌ FAIL (11 histograms failed KS test) (artifact)

target_genie:

• 11 plots failed the KS test against gold.
• Text Differences Between Logs (6077 lines differ)
• Log character count differs by 0% (gold=7408794, new=7366567); within tolerance
• Timing for target_genie: gold=6488s, new=6522s
• Timing within 0% of gold (tolerance 10%)

cascade_history:

• Text Differences Between Logs (2 lines differ)
• Timing for cascade_history: gold=5968s, new=6208s
• Timing within 4% of gold (tolerance 10%)

deep_ecal_gun:

• Text Differences Between Logs (24 lines differ)
• Timing for deep_ecal_gun: gold=4091s, new=4083s
• Timing within 0% of gold (tolerance 10%)

eat_signal:

• Timing for eat_signal: gold=1602s, new=1516s
• Timing within 5% of gold (tolerance 10%)

ecal_pn:

• Text Differences Between Logs (42 lines differ)
• Timing for ecal_pn: gold=6232s, new=6646s
• Timing within 6% of gold (tolerance 10%)

hcal:

• Text Differences Between Logs (2 lines differ)
• Timing for hcal: gold=829s, new=819s
• Timing within 1% of gold (tolerance 10%)

inclusive:

• Text Differences Between Logs (50 lines differ)
• Log character count differs by 0% (gold=21025815, new=21025813); within tolerance
• Timing anomaly for inclusive: new=5140s vs gold=6805s (-24%, tolerance 10%)
• Timing for inclusive: gold=6805s, new=5140s

it_pileup:

• Text Differences Between Logs (46 lines differ)
• Timing for it_pileup: gold=577s, new=593s
• Timing within 2% of gold (tolerance 10%)

kaon_enhanced:

• Text Differences Between Logs (30 lines differ)
• Timing for kaon_enhanced: gold=3122s, new=3063s
• Timing within 1% of gold (tolerance 10%)

reduced_ldmx:

• Text Differences Between Logs (20 lines differ)
• Timing for reduced_ldmx: gold=211s, new=211s
• Timing within 0% of gold (tolerance 10%)

signal:

• Text Differences Between Logs (40 lines differ)
• Timing for signal: gold=1184s, new=1239s
• Timing within 4% of gold (tolerance 10%)

signal_target_al:

• Text Differences Between Logs (36 lines differ)
• Timing for signal_target_al: gold=1047s, new=1029s
• Timing within 1% of gold (tolerance 10%)

target_pn_lyso:

• Text Differences Between Logs (40 lines differ)
• Timing for target_pn_lyso: gold=6455s, new=6529s
• Timing within 1% of gold (tolerance 10%)

target_ti_en:

• Text Differences Between Logs (28 lines differ)
• Timing for target_ti_en: gold=3226s, new=3166s
• Timing within 1% of gold (tolerance 10%)

wab_lhe:

• Text Differences Between Logs (22 lines differ)
• Timing for wab_lhe: gold=6770s, new=6708s
• Timing within 0% of gold (tolerance 10%)

[tvami]

/run-validation

[github-actions]

The validation workflow is running here: https://github.com/LDMX-Software/ldmx-sw/actions/runs/27695331269.

[tomeichlersmith]

small, logical change that I'm worried about affecting the algorithm

[tvami]

/run-validation

[github-actions]

The validation workflow is running here: https://github.com/LDMX-Software/ldmx-sw/actions/runs/27696786470.

[github-actions]

Validation Results

All validation samples passed! ✅

Sample	Status
cascade_history	✅ PASS
deep_ecal_gun	✅ PASS
eat_signal	✅ PASS
ecal_pn	✅ PASS
hcal	✅ PASS
inclusive	✅ PASS
it_pileup	✅ PASS
kaon_enhanced	✅ PASS
reduced_ldmx	✅ PASS
signal	✅ PASS
signal_target_al	✅ PASS
target_genie	✅ PASS
target_pn_lyso	✅ PASS
target_ti_en	✅ PASS
wab_lhe	✅ PASS

cascade_history:

• Text Differences Between Logs (2 lines differ)
• Timing for cascade_history: gold=5968s, new=6374s
• Timing within 6% of gold (tolerance 10%)

deep_ecal_gun:

• Text Differences Between Logs (18 lines differ)
• Timing for deep_ecal_gun: gold=4091s, new=3701s
• Timing within 9% of gold (tolerance 10%)

eat_signal:

• Timing for eat_signal: gold=1602s, new=1563s
• Timing within 2% of gold (tolerance 10%)

ecal_pn:

• Text Differences Between Logs (50 lines differ)
• Timing anomaly for ecal_pn: new=5248s vs gold=6232s (-15%, tolerance 10%)
• Timing for ecal_pn: gold=6232s, new=5248s

hcal:

• Text Differences Between Logs (2 lines differ)
• Timing for hcal: gold=829s, new=826s
• Timing within 0% of gold (tolerance 10%)

inclusive:

• Text Differences Between Logs (36 lines differ)
• Timing for inclusive: gold=6805s, new=6976s
• Timing within 2% of gold (tolerance 10%)

it_pileup:

• Text Differences Between Logs (42 lines differ)
• Timing for it_pileup: gold=577s, new=602s
• Timing within 4% of gold (tolerance 10%)

kaon_enhanced:

• Text Differences Between Logs (40 lines differ)
• Timing anomaly for kaon_enhanced: new=2744s vs gold=3122s (-12%, tolerance 10%)
• Timing for kaon_enhanced: gold=3122s, new=2744s

reduced_ldmx:

• Text Differences Between Logs (20 lines differ)
• Timing for reduced_ldmx: gold=211s, new=210s
• Timing within 0% of gold (tolerance 10%)

signal:

• Text Differences Between Logs (28 lines differ)
• Timing for signal: gold=1184s, new=1183s
• Timing within 0% of gold (tolerance 10%)

signal_target_al:

• Text Differences Between Logs (40 lines differ)
• Timing anomaly for signal_target_al: new=886s vs gold=1047s (-15%, tolerance 10%)
• Timing for signal_target_al: gold=1047s, new=886s

target_genie:

• Text Differences Between Logs (4480 lines differ)
• Timing for target_genie: gold=6488s, new=6556s
• Timing within 1% of gold (tolerance 10%)

target_pn_lyso:

• Text Differences Between Logs (44 lines differ)
• Timing anomaly for target_pn_lyso: new=3689s vs gold=6455s (-42%, tolerance 10%)
• Timing for target_pn_lyso: gold=6455s, new=3689s

target_ti_en:

• Text Differences Between Logs (28 lines differ)
• Timing for target_ti_en: gold=3226s, new=3163s
• Timing within 1% of gold (tolerance 10%)

wab_lhe:

• Text Differences Between Logs (24 lines differ)
• Timing for wab_lhe: gold=6770s, new=6862s
• Timing within 1% of gold (tolerance 10%)