To ensure effective use of resources, NERSC is required to evaluate and adjust allocations quarterly throughout the allocation year (AY).
Who is affected?
Projects that do not use their allocation effectively during the first three quarters of the allocation year will have some of their allocation returned to the reserve pool of their respective DOE Office of Science Program to be redistributed to other projects.
ALCC, Director’s Reserve, Exploratory, and Educational projects are exempt from this scheme. However, ALCC has its own allocation reduction scheme, and the Director’s Reserve program may make reductions at NERSC’s discretion.
How reductions are calculated
NERSC calculates reduction values using the quarterly usage estimates entered in the AY 2025 ERCAP requests. Consistent-use projects (those that selected “I plan to use resources consistently throughout the allocation year”) are set to 25% per quarter. Variable-use projects (those that selected “my usage will vary throughout the allocation year”) use the percentages supplied for each quarter.
Allocation reduction calculations consider only the initial allocation (ERCAP Award). Additional time allocated to a project after the initial award is not considered.
The reduction scheme applies to both CPU and GPU allocations, but each is handled separately.
Exemptions
Project Principal Investigators, PI Proxy, or Project Resource Managers can request exemptions by creating a ticket at the NERSC Online Help Desk and including justification for the request. Requests must be submitted at least two weeks before the reductions are scheduled to take place. The DOE program manager who made the initial award will evaluate requests.
AY 2025 schedule and formulae
For AY 2025 (which runs from January 15, 2025, through January 20, 2026, allocation reductions will be performed on the following dates:
On April 16, 2025
An amount of time equal to the difference between expected usage and time actually charged will be returned to the DOE program’s allocation reserve for redistribution using the following calculation:
Expected Usage (Year to Date) = (initial_allocation) * (Q1% value from ERCAP request)
If Time Charged (YTD) is less than Expected Usage (YTD), allocation will be reduced using the formula:
Reduction = Expected Usage (YTD) – Time Charged (YTD)
On July 16, 2025
An amount of time equal to the difference between expected usage for Q2 and time actually charged in Q2 will be returned for redistribution. The following formula is used in the calculation:
Expected Usage (YTD) = initial_allocation*(Q1% + Q2%) – previous reductions
If Time Charged (YTD) is less than Expected Usage (YTD), allocation will be removed using the formula:
Reduction = Expected Usage (YTD) – Time Charged (YTD)
On October 15, 2025
An amount of time equal to the difference between expected usage for Q3 and time actually charged in Q3 will be returned for redistribution. The following formula is used in the calculation:
Expected Usage (YTD) = initial_allocation*(Q1% + Q2% + Q3%) – previous reductions
If Time Charged (YTD) is less than Expected Usage (YTD), allocation will be removed using the formula:
Reduction = Expected Usage (YTD) – Time Charged (YTD)
If a project that was created in January has zero usage, 100% of its allocation will be removed and returned to the DOE reserve during this, the final quarterly allocation reduction.
Example project and calculations
To illustrate, quarterly calculations for a theoretical example project follow.
Assuming an initial allocation of 1,000 hours and a projected use of 25% per quarter (“I plan to use resources consistently throughout the allocation year”), the example project charges the following hours at each milestone date:
- April 16, 2025 = 50 hours YTD
- July 16, 2025 = 150 hours YTD
- October 15, 2025 = 300 hours YTD
Calculations for each quarter follow.
On April 16
Expected charge YTD
(25% * 1,000) = 250
Actual charge YTD
50
Reduction
(250 – 50) = 200
Adjusted Allocation
(1,000 – 200) = 800
On July 16
Expected charge YTD
(25%+25%)*1,000 – 200 = 500 – 200 = 300
Actual charge YTD
150
Reduction
300 – 150 = 150
Adjusted allocation
800 – 150 = 650
On October 15
Expected charge YTD
(25%+25%+25%)*1,000 – 150 – 200 = 400
Actual charge YTD
300
Reduction
400 – 300 = 100
Adjusted allocation
650 – 100 = 550