fix: warnings for pyodide

Author: gangula-karthik

meson.build

@@ -15,11 +15,19 @@ py = import('python').find_installation(pure: false)
 tempita = files('generate_pxi.py')
 versioneer = files('generate_version.py')
 
-# Find OpenMP dependency
+# Find OpenMP dependency - skip for Pyodide/WebAssembly builds
+is_pyodide_build = false
+cc = meson.get_compiler('c')
+
+# Check if we're building for WebAssembly/Pyodide
+if cc.get_id() == 'clang' and host_machine.cpu_family() == 'wasm32'
+    is_pyodide_build = true
+    message('Detected Pyodide/WebAssembly build - skipping OpenMP')
+endif
+
 openmp_dep = dependency('openmp', required: false)
-if not openmp_dep.found()
+if not openmp_dep.found() and not is_pyodide_build
     # Try to find OpenMP using compiler flags
-    cc = meson.get_compiler('c')
     if cc.has_argument('-fopenmp')
         openmp_dep = declare_dependency(
             compile_args: ['-fopenmp'],
@@ -40,13 +48,17 @@ add_project_arguments(
     language: 'cpp',
 )
 
-# Add OpenMP compile args if available
-if openmp_dep.found()
+# Add OpenMP compile args if available and not building for Pyodide
+if openmp_dep.found() and not is_pyodide_build
     add_project_arguments('-DHAVE_OPENMP', language: 'c')
     add_project_arguments('-DHAVE_OPENMP', language: 'cpp')
     message('OpenMP support enabled')
 else
-    message('OpenMP not found - parallel code will run sequentially')
+    if is_pyodide_build
+        message('OpenMP disabled for Pyodide/WebAssembly build')
+    else
+        message('OpenMP not found - parallel code will run sequentially')
+    endif
 endif
 
 if fs.exists('_version_meson.py')

pandas/_libs/algos.pyx

@@ -11,6 +11,8 @@ from libc.stdlib cimport (
 )
 from libc.string cimport memmove
 
+import sys
+
 import numpy as np
 
 cimport numpy as cnp
@@ -365,6 +367,10 @@ def nancorr(
         float64_t mean, ssqd, val
         float64_t vx, vy, dx, dy, meanx, meany, divisor, ssqdmx, ssqdmy, covxy, corr_val
 
+    # Disable parallel execution in Pyodide/WebAssembly environment
+    if use_parallel and hasattr(sys, "platform") and sys.platform == "emscripten":
+        use_parallel = False
+
     N, K = (<object>mat).shape
     if minp is None:
         minpv = 1

pandas/core/frame.py

@@ -11374,7 +11374,19 @@ def corr(
         mat = data.to_numpy(dtype=float, na_value=np.nan, copy=False)
 
         if method == "pearson":
-            correl = libalgos.nancorr(mat, minp=min_periods, use_parallel=use_parallel)
+            if use_parallel:
+                try:
+                    correl = libalgos.nancorr(mat, minp=min_periods, use_parallel=True)
+                except (ImportError, AttributeError, RuntimeError):
+                    # OpenMP not available or prange failed, fall back to sequential
+                    warnings.warn(
+                        "No parallelism; using sequential (e.g. Pyodide or no OpenMP).",
+                        UserWarning,
+                        stacklevel=find_stack_level(),
+                    )
+                    correl = libalgos.nancorr(mat, minp=min_periods, use_parallel=False)
+            else:
+                correl = libalgos.nancorr(mat, minp=min_periods, use_parallel=False)
         elif method == "spearman":
             correl = libalgos.nancorr_spearman(mat, minp=min_periods)
         elif method == "kendall" or callable(method):