The phrase "are extremely complex to" is correct and usable in written English.
It can be used when describing something that is difficult to understand or deal with, often followed by an action or process that is challenging.
Example: "The algorithms used in machine learning are extremely complex to implement without proper training."
Alternatives: "are highly complicated to" or "are very difficult to".
However these models themselves are extremely complex to code, test, simulate and analyze.
"All of the e-commerce analytics tools on the market are extremely complex to set up and the reports they generate are hard to understand and slow to process," says GoSquared co-founder James Gill.
It is important to reiterate that these tripartite systems of HLA-drug-peptide are extremely complex to model and the relationships between the individual components is not well understood.
In the rugged environment of the engine, precision measurement systems that can withstand high temperatures are extremely complex to design, but can equate to significant fuel savings when done right.
However, such survey programs are extremely complex to organize and administer.
Group dynamics are extremely complex to model particularly in an open group setting where members change from session to session (Morgan-Lopez et al., 2011; Paddock et al., 2011) and no attempt to assess these was included here.
Unlike conventional pharmaceuticals, medicines made of proteins or other biological molecules can be extremely complex to make, often using expensive raw materials or live cells to churn out a product that must then go through elaborate purification.
Given the heterogeneous technology offer and the pricing models currently available in the cloud market it is extremely complex to find the deployment that fits the application requirements and provides the best Quality of Service (QoS) and cost trade-offs.
All the software has been designed for animation professionals, so it is extremely complex to use".
Unfortunately, for many it's extremely complex to manage and deploy," said DigitalOcean VP of Product Shiven Ramji in today's announcement.
Iterative ICI cancellation has been proposed through iterative inversion techniques [7] or turbo processing [8] but is extremely complex to implement.
