mirror of
https://github.com/harvard-edge/cs249r_book.git
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f136f96fd8
Renamed the core physics engine from to to better align with the book's title and pedagogical goals. New features: - Introduced and classes in and . - Digital twins now carry their own attributes (bandwidth, FLOPS) and methods (ridge_point, memory_size). - Global search and replace updated all 16 chapters to use . - Maintained backward compatibility for legacy constants during migration.
120 lines
4.3 KiB
Python
120 lines
4.3 KiB
Python
# test_narrative_invariants.py
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# This test suite protects the "truth" of the textbook.
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# It ensures that the mathematical conclusions drawn in the prose
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# remain valid even as underlying hardware constants are updated.
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import os
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import sys
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import pytest
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project_root = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
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sys.path.append(os.path.join(project_root, 'quarto'))
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from mlsys.constants import (
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ureg,
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SPEED_OF_LIGHT_FIBER_KM_S,
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NETWORK_10G_BW,
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CLOUD_EGRESS_PER_GB,
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CLOUD_ELECTRICITY_PER_KWH,
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PHONE_BATTERY_WH,
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OBJECT_DETECTOR_POWER_W,
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RESNET50_FLOPs,
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A100_MEM_BW,
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MOBILE_NPU_MEM_BW,
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VIDEO_1080P_WIDTH, VIDEO_1080P_HEIGHT, VIDEO_BYTES_PER_PIXEL_RGB, VIDEO_FPS_STANDARD,
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NETWORK_5G_ENERGY_PER_MB_MJ, ENERGY_MOBILENET_INF_MJ,
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MB, GB
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)
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from mlsys.formulas import (
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calc_network_latency_ms,
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calc_monthly_egress_cost,
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calc_fleet_tco,
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calc_bottleneck
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)
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def test_distance_penalty_precludes_cloud():
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"""
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Narrative: "Physics has made Cloud ML impossible for this application."
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Invariant: Round-trip time for 1500km must exceed the 10ms safety budget.
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"""
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distance_km = 1500
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safety_budget_ms = 10
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rtt_ms = calc_network_latency_ms(distance_km)
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assert rtt_ms > safety_budget_ms, \
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f"Narrative Violation: Cloud latency ({rtt_ms:.1f}ms) is now faster than safety budget ({safety_budget_ms}ms)!"
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def test_bandwidth_makes_cloud_streaming_impossible():
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"""
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Narrative: "You need 15x more bandwidth than exists."
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Invariant: 100 cameras require significantly more bandwidth than a 10Gbps link.
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"""
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num_cameras = 100
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raw_bytes_per_sec = (VIDEO_1080P_WIDTH * VIDEO_1080P_HEIGHT * VIDEO_BYTES_PER_PIXEL_RGB * VIDEO_FPS_STANDARD)
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total_bandwidth = num_cameras * raw_bytes_per_sec
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# Check that we exceed 10Gbps link
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assert total_bandwidth > NETWORK_10G_BW, \
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"Narrative Violation: 10Gbps link is now sufficient for 100 raw streams!"
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# Check the "15x" claim (allow some drift, but it should be >10x)
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ratio = total_bandwidth / NETWORK_10G_BW
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assert ratio > 10, \
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f"Narrative Violation: Bandwidth shortage dropped to {ratio:.1f}x (text implies ~15x)"
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def test_energy_gap_favors_edge():
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"""
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Narrative: "Transmitting data is 1000x more energy-expensive than processing it locally."
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Invariant: Transmission energy >> Inference energy.
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"""
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# Energy for 1MB
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data_size = 1 * MB
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tx_energy = NETWORK_5G_ENERGY_PER_MB_MJ * data_size
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npu_energy = ENERGY_MOBILENET_INF_MJ
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ratio = tx_energy / npu_energy
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assert ratio > 500, \
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f"Narrative Violation: Energy gap dropped to {ratio:.1f}x (text says 1000x)!"
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def test_edge_tco_cheaper_than_cloud():
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"""
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Narrative: "Coral Dev Board ... meets requirements at 1/4 the cost of Jetson... vs cloud inference at ~$500K"
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Invariant: Edge TCO < Cloud TCO for high-volume scenario.
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"""
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stores = 500
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cameras = 20
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fps = 15
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years = 3
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# Cloud Cost Reference (from text approximation)
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# 1M inferences/day was $36k/year.
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# Here we have 500 stores * 20 cams * 15 fps = 150,000 inf/sec
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# This volume is massive. Just check Edge vs Edge relative costs first.
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coral_cost = 150 * ureg.dollar
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coral_power = 2 * ureg.watt
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jetson_cost = 600 * ureg.dollar
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jetson_power = 25 * ureg.watt
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coral_tco = calc_fleet_tco(coral_cost, coral_power, stores, years, CLOUD_ELECTRICITY_PER_KWH)
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jetson_tco = calc_fleet_tco(jetson_cost, jetson_power, stores, years, CLOUD_ELECTRICITY_PER_KWH)
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assert coral_tco < jetson_tco, "Narrative Violation: Coral is no longer cheaper than Jetson!"
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ratio = jetson_tco / coral_tco
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assert ratio > 2, f"Narrative Violation: Jetson/Coral cost ratio is {ratio:.1f}x (text implies ~3-4x)"
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def test_battery_tax_depletes_phone():
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"""
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Narrative: "Your single feature has just consumed 30% [or 100%] of the budget."
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Invariant: A 2W continuous load drains a 15Wh battery in < 1 day.
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"""
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runtime = PHONE_BATTERY_WH / OBJECT_DETECTOR_POWER_W
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day = 24 * ureg.hour
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assert runtime < day, "Narrative Violation: Battery now lasts more than a day with continuous ML!"
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assert runtime < (8 * ureg.hour), "Narrative Violation: Battery lasts too long (>8h) for the 'few hours' narrative."
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