Paralithic

Super fast expression evaluator/parser written in Java

Paralithic is a library for parsing and evaluating mathematical expressions. It uses ASM to dynamically generate implementations of the Expression interface representing the expression, with expressions converted directly into Java bytecode for maximum performance, and maximum room for JIT optimization. Paralithic also uses several AOT optimization techniques, such as:

• Evaluating stateless functions with constant arguments at parse time, replacing them with constants.
• Evaluating binary operations with constant operands at parse time, replacing them with constants.
• Combining constants in nested commutative binary operations.

By directly generating bytecode to be executed by the JVM, and with the above optimizations, Paralithic expressions are able to achieve about the same speed as hard-coded ones.

Usage

Parser parser = new Parser(); // Create parser instance.
Scope scope = new Scope(); // Create variable scope. This scope can hold both constants and invocation variables.
scope.addInvocationVariable("x"); // Register variable to be used in calls to #evaluate. Values are passed in the order they are registered.
scope.create("y", 3); // Create named constant y with value 3
Expression expression = parser.parse("x * 4 + pow(2, y)", scope);
expression.evaluate(3); // 20 (3*4 + 2^3 = 20)

Performance

The expression "(2 + ((7-5) * (3.14159 * pow(x, (12-10))) + sin(-3.141)))" was evaluated with x ranging from 0 to 1,000,000 in 3 different expression libraries.

The test was run 20 times to allow the JIT to warmup and optimize as much as possible, then 20 more iterations were timed and averaged. The "Aggregate" values are the summed values of all iterations in the test. The aggregate is mainly to prevent HotSpot JIT from optimizing out calls to evaluation altogether.

The native and native (simplified) tests each tested a hard-coded method containing the expanded and simplified expression, respectively.

Testing native (simplified)...
Avg for 20 iterations of 1000000 evaluations: 3.754001105263158ms
Aggregate: 8.377560766985067E19

Testing Paralithic...
Avg for 20 iterations of 1000000 evaluations: 4.712781315789473ms
Aggregate: 8.377560766985067E19

Testing native...
Avg for 20 iterations of 1000000 evaluations: 9.540265526315789ms
Aggregate: 8.377560766985067E19

Testing parsii...
Avg for 20 iterations of 1000000 evaluations: 38.82801278947368ms
Aggregate: 8.377560766985075E19

Testing exp4j...
Avg for 20 iterations of 1000000 evaluations: 207.5611217368421ms
Aggregate: 8.377560766985067E19

Results are from test run on an AMD Ryzen 9 3900X.

Paralithic generated the following class from the input function (decompiled with FernFlower):

public class ExpressionIMPL_0 implements Expression {
    public ExpressionIMPL_0() {
    }

    public double evaluate(double[] var1) {
        return 1.9994073464449005D + 6.28318D * NativeMath.pow2(var1[0]);
    }
}

License

Paralithic is licensed under the GNU General Public License version 3.0 (GPLv3).

Paralithic is a "fork" of a modified version of Parsii, licensed under the MIT license.