u/OkEmu7082

in quantum chem code, there are a lot of recompute on the fly designs to trade ram usage for flop, such as the ERI, especially the plain four indexed one as opposed to the RI/CD one, which reduces the ram scaling but not the cpu cost scaling. another example is in the mp2 energy and gradient, the t2 and lambda2 can be recomputed so one never stores an o^2 v^2 obj in RIMP2.

what else? is there a nice review paper that is not specific to a single method but use various examples to discuss something like a general flop/ram ratio and analyze the benefit/trade-off of computing stuffs on the fly

EDIT: i think some other good examples are 1 direct CI, and knowles handy CI, which assembles CI matrix elements on the fly, and in EOMCC the matrix elements of Hbar are also on the fly, and 2FCIQMC, which trades ram for flop even more drastically

in principle, when computing gradients for multiple roots, a lot of stuffs can be computed only for once and reused accross multiple roots, for example the integral derivatives like dERI/dx, dS/dx,dHcore/dx that are universally needed and also the orbital response eqn's LHS, df(k)/dk which is almost universal to all es methods' since the energy is usually not stationary wrt to orbital rotation, and a sa-casscf specific stuff, the electronic integrals in casscf MOs, which is the one the gradient code uses, and is not the one in HF canonical MOs that other post HF methods use

can anyone experienced with pyscf tell me what can i set pyscf to reuse and how to set it for typical excited state methods like sa-casscf and cis/tddft? and share example input files?

in principle, when computing gradients for multiple roots, a lot of stuffs can be computed only for once and reused accross multiple roots, for example the integral derivatives like dERI/dx, dS/dx,dHcore/dx that are universally needed and also the orbital response eqn's LHS, df(k)/dk which is almost universal to all es methods' since the energy is usually not stationary wrt to orbital rotation, and a sa-casscf specific stuff, the electronic integrals in casscf MOs, which is the one the gradient code uses, and is not the one in HF canonical MOs that other post HF methods use

can anyone experienced with pyscf tell me what can i set pyscf to reuse and how to set it for typical excited state methods like sa-casscf and cis/tddft? and share example input files?

the CC lagrangian generally takes the form L = E + lambda' R(t) + z' f(k) where t is the amplitude and the k is the orbtial rotation, the R is the residue eqn of the cc projection eqn and the f(k) is the term related to orbital response

to solve the multipliers lambda and z the full adjoint eqn is a system of 2 eqn and 2 unknowns, 0=pL/pt=pE/pt + lambda' pR/pt and 0= pL/pz =pE/pz +pR/pz + pf/pz

in practice typical code like psi4 does not genuinely solve this system of adjoint eqn together, but rather the lambda eqn first and then the response one, this is achieved by takes pR(t)/pk =0 so that z does not influence the lambda eqn

my question is, is pR(t)/pk =0 an approximation or is it exact? if exact, why?

it seems the double projection eqn of CC2, <D|[F,T2]+H|HF>=0 is exactly the same as the one of the MP2, if i do the MP2 by reusing the CC2's code(in production code is it done in this way?) to do t2=t2(t1) to project the doubles out without doing the singles, do i get exactly MP2?

the CC2 and CCD have straght forward LRCC and EOM CC excited state fomulism, why is it not so straightforward for MP2? if i use the t2 obtained in the above way to do Hbar = e^-t H e^t, or apply LR to get the jaccobian and daigonalize to get excited state what will happen?

https://preview.redd.it/yng8e5thddfh1.png?width=1920&format=png&auto=webp&s=88cc21d50430423cbbddb90b671a17c42e89e1d9

due to some issue, i have to delete simcity and re download to update, after doing that and passing the tutorial i can no longer find the log into ea account options that used to be there in the settings, does anyone else expereince that? how to log into my old city

in unitary CCS the T1-T1' is basically the generator of orbital rotation, so the only difference between UCCS and HF seems to be that HF absorbs the orbital rotation into the MO coeff, and the UCCS keeps it in the T1 amplitude, one can imagine a similar equivalence between EOM-UCCS and TDHF, which has deexcitation over CIS ,does anyone know if this is true and any paper that confirms that?

is it a good idea to build ai rigs with old 2080ti modified to 22gb for local llm and renting for profit in large numbers? since it is old and the price has been stablized

is there any readily available sulution that i can purchase? has anyone done this? what is your experience?

I’m looking for a game-bot development framework that runs natively on a rooted Android phone and provides APIs for:

• Screen interactions: tap, swipe/drag, screenshots, etc.
• App control: launch, close/force-stop, restart
• Ideally, a floating start/stop button and basic error/retry handling

I want to write only the high-level game-bot logic, without dealing with ADB or Android automation plumbing.

Ideally, these APIs would be exposed through a clean abstraction similar to a trait or an (abstract) base class.

what are the open source packages that are most complete and advanced in terms of energy and gradient availability of EOM-CCSD and CC2 CC3 excited state

https://preview.redd.it/g21ct2wwmpbh1.png?width=545&format=png&auto=webp&s=91b519be24f32a5894f1694895b331c159b2b1fd

does anyone have experience with this pattern of stalking? why does he use MMS, what's probably inside? how to effectively gather evidence( i have reported to police but they do not seem to be investigating)

if my cpu has hyperthreading (HT)capability(one physical gives two logical threads), when planning for memory locality should i simply divide the thread private memory capacity(L1 cache, and registers) by two? are there further implications? or should i simply run my cpp parallel program with no two threads coming from a same core( is there a way to run the program switching off HT or should i switch off HT in bios when booting my computer)

to consider a concrete example, if i do parallelized tiled matrix multiplication, and i intend to fit my matrix tiles into registers private to a core, how to do that when my cpu has HT? should i simply divide the capacity of registers private to a core by two?

the stateless ABC interface is similar to rust trait in the sense that it allows default behavior in base class by non pure virtual functions, but it is run time polymorphism only. the template + concept does not seem to allow default behavior in "base type"

in modern cpp, how to use boiler plates to get as close as possible to Rust's traits, which is like a stateless ABC interface but is compile time polymorphism?

is the latest update this week no longer compatible with google pixel 1?

is the simplest solution to have internet access unrestricted by the GFW in China just to purchase international data with my current US carrier?

it seems very few people mention this. is it because it will not work? i understand the price is high, but i only need it for occasional email checking and US banking app and social media

is the simplest solution to have internet access unrestricted by the GFW in China just to purchase international data with my current US carrier?

it seems very few people mention this. is it because it will not work? i understand the price is high, but i only need it for occasional email checking and US banking app and social media

can esim be used to make sure that my network will not be affected by the great firewall in china？if not what is commonly used for this purpose?

how to precisely understand the basic reason behind EOMCC and LRCC giving the same result?

the CIS is a CI formalism, the TDHF is a response formalism, also they are both based on HF, but they give different results, why CC's exponential anzatz bring the CI and LR into equivalence?

is it like, in linear algebra equivalent to a type of operator whose next eigen vector can be expressed as R acting on the previous one?

what are the other methods that preserve this equivalence, CC2,CC3, ADC?

any recommendation on must read papers about it and a summary of salient point is greatly appreciated

i hear if i do a secodary master in germany and later work in Germany, costs related to study can be used to cancel income tax

if my program charges tuition, what should i do to reserve this option?

does it also cover the cost related to dorm or renting apartment/hostel near the uni for studying?

do those all apply to non EU international students?

i think so for several reasons

1. LLMs are nothing but a more sophisticated linear regression model, they rely on empirical fitting and are intrinsically bad at tasks that require first principle derivation, in practice, ai assistant is effective only at low level coding tasks like filling a function implementation when i lay down a function signiture, writing tests and finding bugs, for high level design choices and some performance optimizations that require first principle reasoning it still struggles.

2 the ai tools have been heavily subsidized in the past, because those ai firms are competing for market shares, when this is over and the token price come back to the real level, the market will realize for many tasks, hiring a live human is cheaper than the token cost

what do you think?