FFM is the new API trying to replace JNI and jep is here It is basically calling calling functions outside of JVM or accessing memory not managed by JVM. I wanted to test can FFM beat regular Java API, below you can find a simple test doing math sin with FFM and with regular Math.sin
import java.lang.foreign.FunctionDescriptor;
import java.lang.foreign.Linker;
import java.lang.foreign.MemorySegment;
import java.lang.foreign.SymbolLookup;
import java.lang.foreign.ValueLayout;
public class FFMSinTest {
public static void main(String[] args) throws Throwable {
Linker linker = Linker.nativeLinker();
SymbolLookup stdlib = linker.defaultLookup();
// Locate the "sin" function in the C math library
MemorySegment sinAddress = stdlib.find("sin").orElseThrow();
FunctionDescriptor descriptor = FunctionDescriptor.of(ValueLayout.JAVA_DOUBLE, ValueLayout.JAVA_DOUBLE);
var sinHandle = linker.downcallHandle(sinAddress, descriptor);
double angle = Math.PI / 4; // 45 degrees in radians
// Timing Java's Math.sin()
long javaStartTime = System.nanoTime();
for (int i = 0; i < 1_000_000; i++) {
double result = Math.sin(angle);
}
long javaEndTime = System.nanoTime();
long javaDuration = javaEndTime - javaStartTime;
// Timing C sin via FFM
long ffmStartTime = System.nanoTime();
for (int i = 0; i < 1_000_000; i++) {
double result = (double) sinHandle.invoke(angle);
}
long ffmEndTime = System.nanoTime();
long ffmDuration = ffmEndTime - ffmStartTime;
System.out.println("Java Math.sin() took: " + javaDuration / 1_000_000.0 + " ms");
System.out.println("C sin (FFM) took: " + ffmDuration / 1_000_000.0 + " ms");
}
}
And result is
Java Math.sin() took: 4.8677 ms
C sin (FFM) took: 78.9172 ms
In my laptop, lesson is “calling outside JVM is not a cheap process” 🤓