From dadde72a4c914ecfc81583ff8aec57b91c56ec4a Mon Sep 17 00:00:00 2001
From: thurinj <julienthurin06@gmail.com>
Date: Wed, 27 Nov 2024 12:34:52 +1100
Subject: [PATCH] Optimized C code by moving a variable outside of a loop.

It seems that the repeated access to `sources(isrc,ig)` causes a slow-down that can be easily avoided by caching the source as:

```python3
double source_val = sources (isrc, ig)
```

From local test on an M1 mac, this yield a speedup of about ~1.18.

Changed variable name for consistency
---
 mtuq/misfit/waveform/c_ext_L2.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mtuq/misfit/waveform/c_ext_L2.c b/mtuq/misfit/waveform/c_ext_L2.c
index cbc6f7245..f1f43518c 100644
--- a/mtuq/misfit/waveform/c_ext_L2.c
+++ b/mtuq/misfit/waveform/c_ext_L2.c
@@ -209,8 +209,9 @@ static PyObject *misfit(PyObject *self, PyObject *args) {
 
           // Sum cross-correlations of all components being considered
           for (ig=0; ig<NG; ig++) {
+            double source_val = sources (isrc, ig);
             for (it=0; it<NPAD; it++) {
-                cc(it) += greens_data(ista,ic,ig,it) * sources(isrc,ig);
+                cc(it) += greens_data(ista,ic,ig,it) * source_val;
             }
           }
         }