Job Runtime vs Compute Time

Simscope optionally supports separate job runtime and compute time Job fields.

• If runtime and finish_time fields are omitted from the job JSON, Simscope assumes:
  runtime_ms = compute_ms

Purpose of separating Runtime and Compute time

• compute_ms — tracks the compute (ie CPU) time of the job. This is used to calculate CPS (cycles-per-second). Sometimes this is called machine time (or machine hours/machine days).
• runtime_ms — tracks the wallclock duration of the job. This allows separating out non-compute events like license checkout, network/disk load, or pre/post-simulation tasks.

Simscope can chart both job compute time and job runtime fields.

Job time limit

Note: Individual jobs are currently limited to a maximum duration (either runtime or compute) of 24 days.

• If they exceed this limit, the job will be rejected during import.

Regressions, however, do not have a limit on their duration.

Example Job with separate compute and runtime

This job has separate compute and runtime fields:

Calculating runtime field

start_time and finish_time

If your job JSON has both start_time and finish_time fields, runtime is automatically inferred as:

# Job runtime (milliseconds)
job.runtime_ms = (job.finish_time - job.start_time) * 1000

This example JSON infers a runtime_ms of 9080000 milliseconds (ie 15 min, 8 sec) and a compute_ms of 780200 milliseconds (ie 13 min):

{
    "start_time": "2021-05-07T02:00:10-05:00",
    "finish_time": "2021-05-07T02:15:18-05:00",
    "compute_ms": 780200
    ...
}

Explicit compute_ms field

If you want to specify job runtime and compute explicitly (in milliseconds), your JSON should have start_time, compute_ms, and runtime_ms fields.

This example has a compute time of 45.238 seconds and a runtime of 47.5 seconds:

{
    "start_time": "2021-05-07T02:00:10.000111-05:00",
    "compute_ms": 45238,
    "runtime_ms": 47500
    ...
}

CPS calculation

CPS (cycles per second) is a simple metric to track simulation performance.

• Over time, if this reduces, you are using extra (ie wasting) compute to run the same number of simulation cycles.
• CPS can be charted, to track it's value over time.

CPS is calculated within Simscope as:

cps = total_cycles / (total_compute_ms / 1000)

Notes:

• Simscope uses the compute_ms value (job CPU time), not runtime_ms (job wallclock runtime) for CPS calculation.
• Simscope ignores any jobs where cycles = 0.
  • This prevents non-simulations (e.g. lint, compile, etc) from affecting CPS.

CPS Pass-only vs Pass+Fail

Simscope calculates CPS using two different methods:

• CPS Pass-only — cycles-per-second among pass jobs only.
  • This is the recommended use for tracking long term performance, as it is a more stable value, unaffected by early failing simulations, which usually.
• CPS Pass+fail — cycles-per-second among all matching jobs.