apg: add SD_LOG_CFG_DELTA_NORM

Author: stduhpf

stable-diffusion.cpp

@@ -1196,7 +1196,18 @@ class StableDiffusionGGML {
 
             float* deltas = vec_denoised;
 
-            // https://arxiv.org/pdf/2410.02416
+            // APG: https://arxiv.org/pdf/2410.02416
+
+            bool log_cfg_norm                 = false;
+            const char* SD_LOG_CFG_DELTA_NORM = getenv("SD_LOG_CFG_DELTA_NORM");
+            if (SD_LOG_CFG_DELTA_NORM != nullptr) {
+                std::string sd_log_cfg_norm_str = SD_LOG_CFG_DELTA_NORM;
+                if (sd_log_cfg_norm_str == "ON" || sd_log_cfg_norm_str == "TRUE") {
+                    log_cfg_norm = true;
+                } else if (sd_log_cfg_norm_str != "OFF" && sd_log_cfg_norm_str != "FALSE") {
+                    LOG_WARN("SD_LOG_CFG_DELTA_NORM environment variable has unexpected value. Assuming default (\"OFF\"). (Expected \"ON\"/\"TRUE\" or\"OFF\"/\"FALSE\", got \"%s\")", SD_LOG_CFG_DELTA_NORM);
+                }
+            }
             float apg_scale_factor = 1.;
             float diff_norm        = 0;
             float cond_norm_sq     = 0;
@@ -1224,7 +1235,7 @@ class StableDiffusionGGML {
                         delta += guidance.apg.momentum * apg_momentum_buffer[i];
                         apg_momentum_buffer[i] = delta;
                     }
-                    if (guidance.apg.norm_treshold > 0) {
+                    if (guidance.apg.norm_treshold > 0 || log_cfg_norm) {
                         diff_norm += delta * delta;
                     }
                     if (guidance.apg.eta != 1.0f) {
@@ -1233,6 +1244,9 @@ class StableDiffusionGGML {
                     }
                     deltas[i] = delta;
                 }
+                if(log_cfg_norm){
+                    LOG_INFO("CFG Delta norm: %.2f", sqrtf(diff_norm));
+                }
                 if (guidance.apg.norm_treshold > 0) {
                     diff_norm = sqrtf(diff_norm);
                     if (guidance.apg.norm_treshold_smoothing <= 0) {