trying to index using the pointers offset to win speed

Author: ZocoLini

modules/mexpreval/src/lib.rs

@@ -11,6 +11,9 @@ thread_local! {
     static CONTEXT: RefCell<Context<'static>> = RefCell::new(Context::new());
 }
 
+static Y: [&str; 8] = ["y1", "y2", "y3", "y4", "y5", "y6", "y7", "y8"];
+static P: [&str; 8] = ["p1", "p2", "p3", "p4", "p5", "p6", "p7", "p8"];
+
 #[allow(clippy::missing_safety_doc)]
 #[no_mangle]
 pub unsafe extern "C" fn eval_f_exprs(
@@ -38,31 +41,24 @@ pub unsafe extern "C" fn eval_f_exprs(
             let mut ctx = ctx.borrow_mut();
 
             for (i, expr) in y.iter().enumerate() {
-                ctx.var(format!("y{}", i + 1), *expr);
+                ctx.var(Y[i], *expr);
             }
 
             for (i, param) in params.iter().enumerate() {
-                ctx.var(format!("p{}", i + 1), *param);
-            }
-
-            if exprs_cache.is_empty() {
-                let c_str = CStr::from_ptr(exprs[0]);
-                let s = c_str.to_str().unwrap();
-                let expr = Expr::from_str(s).unwrap_or_else(|e| panic!("Error parsing expresion {}: {}", s, e));
-                exprs_cache.push(expr);
+                ctx.var(P[i], *param);
             }
 
             for (i, ptr) in exprs.iter().enumerate() {
-                let index = ptr.offset_from(exprs[0]) as usize;
-                
-                if exprs.len() < index {
+                let index = exprs[0].offset_from(*ptr) as usize;
+
+                if exprs_cache.len() <= index {
                     let c_str = CStr::from_ptr(*ptr);
                     let s = c_str.to_str().unwrap();
                     let expr = Expr::from_str(s).unwrap_or_else(|e| panic!("Error parsing expresion {}: {}", s, e));
 
                     exprs_cache.push(expr);
                 }
-                
+
                 let expr = &exprs_cache[index];
 
                 ydot[i] = expr