I know slots is something like the batch size. What is the usage scenario of SetSlots method? In a machine learning application, the size of cipher text will become smaller due to downsampling, can OpenFHE change batch size or slots dynamically to enable sparse packing and then make bootstrap faste…

SetSlots can be used to treat the current CKKS ciphertext as a sparse ciphertext (subring element). However, internally this means that a smaller vector has to be cloned as many times as needed to fill the maximum number of slots (half the ring dimension in CKKS). If this ciphertext is not set up th…

Yep, I guess you can [image] Difference between sparse/full packing FHE Questions Hello, I have a question about the types of packing in CKKS. There are two examples: sparse and full. I got that full packing uses all the slots of the ciphertext, while sparse does not. M…

Thanks for the explanation. Because the size of valid ciphertext is changed in my application. When it becomes smaller, before doing bootstrap, I use setSlots method to set to the small value(the size of currently valid cipher text), but after bootstrap, the value is incorrect. For example: The ri…

On which numSlot did you run the bootstrap setup?

When SetSlots is set to a smaller value, you want to make sure that the sparsely packed ciphertext is a proper subring element for the desired number of slots. For example, let N be the ring dimension and n the desired number of slots, a subring element with n slots is formed by cloning the n-sized …

In addition to proper cloning of the ciphertext, EvalBootstrapSetup and EvalBootstrapKeyGen should be called for that value of numSlots, as pointed out by @narger .

after clear/rotate/addition, it works, thanks.

what is the cloned format? a0b0c0 or abcabc?

Cloning means repetition, so your input will be repeated abcabc, in the sense that you will have batch_size | batch_size | … | batch_size for the ring_dimension / batch_size times.

Another question. If the valid data in the ciphertext is abc, and N=32. The number of valid data cannot be divided by N. How to replicate it in this case?

@Knightley please ask in a new topic as this is a new question

OpenFHE SetSlots method: what is the usage scenario?

Library Questions

Knightley June 18, 2025, 2:34am 14

ok. When the valid data length is an odd number, how to replicate before SetSlots?

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OpenFHE SetSlots method: what is the usage scenario?

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