Allocation Reductions

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.

Time must be redistributed because many projects fall behind early in the year while others run low on time quickly. Reductions and reallocations allow Perlmutter to be used productively throughout the year while reducing the long queue wait times later in the year. 

The issue is illustrated in the table below, which shows how many projects were on pace to use 90 percent or more of their full (GPU) initial allocation in 2024 and how many had already used 90% or more of theirs. The mismatch between usage and need is readily apparent.

Removed time is returned to the appropriate program reserve for DOE program managers to redistribute at their discretion.  Projects that have time removed can request additional time if needed from their DOE allocation manager via the NERSC ticketing system.

Allocation reductions are calculated based on the estimated quarterly usage entered in allocation proposals. (If the center-wide aggregate estimates are too heavily weighted to a given quarter, NERSC will work with users and program managers to address the situation early in the year.)

Projects will not be subject to reductions in the first 60 days following their creation. 

ALCC, Director's Reserve, Exploratory, and Educational projects are exempt from this reduction. However, ALCC has its own allocation reduction scheme, and the Director's Reserve program may make reductions at NERSC's discretion.

Allocation Year 2025

The following schedule will be used for Allocation Year 2025 (which runs from January 15, 2025, through January 20, 2026). Allocation reductions will be performed on

• April 16, 2025
• July 16, 2025
• October 15, 2025

NERSC uses the quarterly usage estimates entered in the AY 2025 ERCAP requests to calculate reduction values. If a project selected "I plan to use resources consistently throughout the allocation year, " the quarterly usage was set to 25% per quarter. If it selected "My usage will vary throughout the allocation year, " we use the percentage of usage entered for each quarter. 

This reduction scheme applies to both CPU and GPU allocations, but each is handled separately.

The DOE program manager who made the initial award will evaluate requests for exemptions. Project Principal Investigators, PI Proxy, or Project Resource Managers can request exemptions by creating a ticket at https://help.nersc.gov and including justification for the request. Requests must be submitted at least two weeks before the reductions are scheduled to take place. 

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. We will use the following calculation:

• Expected Usage = (initial_allocation) * (Q1% value from ERCAP request)
• If Time Charged is less than Expected Usage, allocation will be removed using the formula: 
  • Reduction = Expected Usage - Time Charged

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 (Year to Date) = 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 - Time Charged

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 - Time Charged
• If a project that was created in January has zero usage, 100% of its allocation will be removed and returned to the DOE reserve.

Only the Initial Allocation (ERCAP Award) is considered in these calculations. Additional time allocated to a project after the initial award has no effect.

Example

Initial Allocation: 1,000
Estimated Usage: Q1=25%, Q2=25%, Q3=25%, Q4=25%
Hours Charged as of April 16, 2025 = 50 
Hours Charged as of July 16, 2025 = 150
Hours Charged as of October 15, 2025 = 300
(YTD = Year to Date)

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