Accept start point

src/shmem4py/shmem.py

@@ -872,9 +872,27 @@ def _ceildiv(p: int, q: int) -> int:
 # ---
 
 
+def _parse_stride(st):
+    if isinstance(st, int):
+        stride = st
+        start = [0]
+    elif isinstance(st, tuple):
+        stride, start = st[1], list(st[0])
+
+    return stride, start
+
 def _parse_rma(target, source, size=None, tst=1, sst=1):
-    tdata, tlen, ttype = _getbuffer(target, readonly=False)
-    sdata, slen, stype = _getbuffer(source, readonly=True)
+    if isinstance(tst, tuple): assert target.ndim == len(tst[0])
+    if isinstance(sst, tuple): assert source.ndim == len(sst[0])
+    tst, tstart = _parse_stride(tst)
+    sst, sstart = _parse_stride(sst)
+
+    if tstart != [0]:
+        tdata, tlen, ttype = _getbuffer(target[*tstart[:-1],tstart[-1]:], readonly=False)
+        sdata, slen, stype = _getbuffer(source[*sstart[:-1],sstart[-1]:], readonly=True)
+    else:
+        tdata, tlen, ttype = _getbuffer(target, readonly=False)
+        sdata, slen, stype = _getbuffer(source, readonly=True)
 
     assert ttype == stype
     ctype = ttype
@@ -884,8 +902,7 @@ def _parse_rma(target, source, size=None, tst=1, sst=1):
     if size is None:
         size = min(tsize, ssize)
     else:
-        assert size <= tsize
-        assert size <= ssize
+        assert size >= 0
 
     return (ctype, tdata, sdata, size)
 
@@ -901,6 +918,8 @@ def _shmem_rma(ctx, name, target, source, size, pe):
 
 def _shmem_irma(ctx, name, target, source, tst, sst, size, pe):
     ctype, target, source, size = _parse_rma(target, source, size, tst, sst)
+    tst, _ = _parse_stride(tst)
+    sst, _ = _parse_stride(sst)
     return _shmem(ctx, ctype, f'i{name}')(target, source, tst, sst, size, pe)