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To add to the examples, Truffle currently has interpreters for unmanaged languages such as C/Fortran (with Sulong), dynamic languages such as Ruby and JS, stati

by eregon 10y ago

To add to the examples, Truffle currently has interpreters for unmanaged languages such as C/Fortran (with Sulong), dynamic languages such as Ruby and JS, statistics/math like R and functional like Clojure. The interopability is done in a way that does not need a common representation or object layout. > I wouldn't use Rust for the syntax; I'd use it because I want properties like complete memory safety, manual control over memory allocation, easy (and fast!) access to C libraries, and short startup time. These are all things that Truffle explicitly does not deliver. Truffle itself does not do it, but it is possible to have a Truffle interpreter with these requirements. Memory safety can be enforced at the frontend compiler level like Rust does I believe. Memory can be allocated directly with Unsafe or calling libc functions. GNFI [1] allows for fast calls to native libraries. Startup can be improved radically with SubstrateVM, but it is currently closed-source. There are many ways to improve the JVM startup, but not necessarily convenient (but then you don't need to wait to compile your program either to start running it). [1] http://dl.acm.org/citation.cfm?id=2500832 http://dl.acm.org/citation.cfm?id=2500832

nostrademons 10y ago
The big question is "Would you want to use this in a mission-critical project?" Emscripten lets you write webapps in C, for example, but outside of sharing common libraries across server/Android/iOS/web clients, few people use it. Pretty much every professional job I've had used polyglot programming of some sort - when I was in financial software it was mixed Java/C/Fortran numerics, when I founded my first startup it was polyglot Javascript/ActionScript, and at Google it was a large server that was first Python/C++ and then Java/C++. The boundary between languages is always problematic. And the reason for that is because you choose memory layout to make certain trade-offs around the access patterns for that data. Do you inline data structures in a vector, or chase pointers? Do objects carry their type information with them so you can manipulate them dynamically, or do they throw it away at compile-time for greater efficiency? Do you get O(1) string indexing or native UTF-8? Do you allocate on the stack or the heap? Do you copy, borrow, move, or COW? And then when you go to switch representations to call into another language, you pay a cost to convert all the data structures you might be touching. In many cases, that cost could be more than you saved by using optimized representations in the first place.
- thomaswue 10y ago
  The idea of Truffle language interoperability is to avoid switching the representation at the language boundary. Objects carry their type information with them that includes the semantics on how to access their properties. This also allows Truffle to fake up the existence of an object without actually performing allocations (e.g., a table in raw buffer format can be interpreted as an array of objects). This clear separation of logical and physical layout enables efficient data representation in the context of higher level languages that typically suffer from pointer chasing and object header overheads.
  - nostrademons 10y ago
    Right, and my point is that this won't work unless you dictate a common memory layout for all Truffle objects. And if you do that, then you lose the ability to make trade-offs about object representation that depend upon access patterns that only the programmer can know. The whole reason we have different programming languages is because not all domains of computation face the same trade-offs.
    - thomaswue 10y ago
      It works without common memory layout between Truffle languages. It even simplifies the ability to use diverse physical memory layouts within the same language. The programmer specifies the logical layout based on the semantics of a language. The runtime decides how to map this logical layout onto the physical hardware. It can take into account the trade-offs the programmer decided to choose.
      - nostrademons 10y ago
        Right, and my point is that the reason people continue to use C++ or Rust over JVM languages is because there are some use-cases where the JVM's decision about how to map the logical layout onto physical memory causes unacceptably high memory usage and/or cache misses, or prevents them from taking advantage of clever serialization formats (Cap'n Proto, for example, loses much of its performance benefits on the JVM without the use of sun.misc.unsafe). Will Truffle allow the programmer to override Graal's decisions on this and manually specify memory layout? And if so, how are conversions between different language formats specified? If you already buy the JVM's premise of "just let the compiler do it, we'll figure out the most efficient representation", then this is a non-issue. But there are still programmers out there who believe that Rust or C++ or Go or CPython or whatever presents a better memory layout for the tasks that they wish to accomplish, or language designers who think they can do better than all of the above, and these are the users that Graal+Truffle is trying to win over. What's the story for them?

by eregon 10y ago

nostrademons 10y ago

The big question is "Would you want to use this in a mission-critical project?" Emscripten lets you write webapps in C, for example, but outside of sharing common libraries across server/Android/iOS/web clients, few people use it. Pretty much every professional job I've had used polyglot programming of some sort - when I was in financial software it was mixed Java/C/Fortran numerics, when I founded my first startup it was polyglot Javascript/ActionScript, and at Google it was a large server that was first Python/C++ and then Java/C++. The boundary between languages is always problematic. And the reason for that is because you choose memory layout to make certain trade-offs around the access patterns for that data. Do you inline data structures in a vector, or chase pointers? Do objects carry their type information with them so you can manipulate them dynamically, or do they throw it away at compile-time for greater efficiency? Do you get O(1) string indexing or native UTF-8? Do you allocate on the stack or the heap? Do you copy, borrow, move, or COW? And then when you go to switch representations to call into another language, you pay a cost to convert all the data structures you might be touching. In many cases, that cost could be more than you saved by using optimized representations in the first place.

thomaswue 10y ago
The idea of Truffle language interoperability is to avoid switching the representation at the language boundary. Objects carry their type information with them that includes the semantics on how to access their properties. This also allows Truffle to fake up the existence of an object without actually performing allocations (e.g., a table in raw buffer format can be interpreted as an array of objects). This clear separation of logical and physical layout enables efficient data representation in the context of higher level languages that typically suffer from pointer chasing and object header overheads.
- nostrademons 10y ago
  Right, and my point is that this won't work unless you dictate a common memory layout for all Truffle objects. And if you do that, then you lose the ability to make trade-offs about object representation that depend upon access patterns that only the programmer can know. The whole reason we have different programming languages is because not all domains of computation face the same trade-offs.
  - thomaswue 10y ago
    It works without common memory layout between Truffle languages. It even simplifies the ability to use diverse physical memory layouts within the same language. The programmer specifies the logical layout based on the semantics of a language. The runtime decides how to map this logical layout onto the physical hardware. It can take into account the trade-offs the programmer decided to choose.
    - nostrademons 10y ago
      Right, and my point is that the reason people continue to use C++ or Rust over JVM languages is because there are some use-cases where the JVM's decision about how to map the logical layout onto physical memory causes unacceptably high memory usage and/or cache misses, or prevents them from taking advantage of clever serialization formats (Cap'n Proto, for example, loses much of its performance benefits on the JVM without the use of sun.misc.unsafe). Will Truffle allow the programmer to override Graal's decisions on this and manually specify memory layout? And if so, how are conversions between different language formats specified? If you already buy the JVM's premise of "just let the compiler do it, we'll figure out the most efficient representation", then this is a non-issue. But there are still programmers out there who believe that Rust or C++ or Go or CPython or whatever presents a better memory layout for the tasks that they wish to accomplish, or language designers who think they can do better than all of the above, and these are the users that Graal+Truffle is trying to win over. What's the story for them?