core: irrt add unchecked ndarray slicing

nac3core/irrt/irrt/numpy/ndarray_subscript.hpp

@@ -0,0 +1,137 @@
+#pragma once
+
+#include <irrt/slice.hpp>
+#include <irrt/numpy/ndarray_def.hpp>
+#include <irrt/numpy/ndarray_basic.hpp>
+
+namespace {
+typedef uint8_t NDSubscriptType;
+
+extern "C" {
+const NDSubscriptType INPUT_SUBSCRIPT_TYPE_INDEX = 0;
+const NDSubscriptType INPUT_SUBSCRIPT_TYPE_SLICE = 1;
+}
+
+struct NDSubscript {
+    // A poor-man's enum variant type
+    NDSubscriptType type;
+
+    /*
+        if type == INPUT_SUBSCRIPT_TYPE_INDEX => `slice` points to a single `SizeT`
+        if type == INPUT_SUBSCRIPT_TYPE_SLICE => `slice` points to a single `UserRange<SizeT>`
+
+        `SizeT` is controlled by the caller: `NDSubscript` only cares about where that
+        slice is (the pointer), `NDSubscript` does not care/know about the actual `sizeof()`
+        of the slice value.
+    */
+    uint8_t* data;
+};
+
+namespace ndarray {
+    namespace util {
+        template<typename SizeT>
+        SizeT deduce_ndims_after_slicing(SizeT ndims, SizeT num_subscripts, const NDSubscript* subscripts) {
+            irrt_assert(num_subscripts <= ndims);
+
+            SizeT final_ndims = ndims;
+            for (SizeT i = 0; i < num_subscripts; i++) {
+                if (subscripts[i].type == INPUT_SUBSCRIPT_TYPE_INDEX) {
+                    final_ndims--; // An index demotes the rank by 1
+                }
+            }
+            return final_ndims;
+        }
+    }
+
+    // To support numpy "basic indexing" https://numpy.org/doc/stable/user/basics.indexing.html#basic-indexing
+    // "Advanced indexing" https://numpy.org/doc/stable/user/basics.indexing.html#advanced-indexing is not supported
+    //
+    // This function supports:
+    //   - "scalar indexing",
+    //   - "slicing and strides",
+    //   - and "dimensional indexing tools" (TODO, but this is really easy to implement).
+    //
+    // Things assumed by this function:
+    // - `dst_ndarray` is allocated by the caller
+    // - `dst_ndarray.ndims` has the correct value (according to `ndarray::util::deduce_ndims_after_slicing`).
+    //   - ... and `dst_ndarray.shape` and `dst_ndarray.strides` have been allocated by the caller as well
+    //
+    // Other notes:
+    // - `dst_ndarray->data` does not have to be set, it will be derived.
+    // - `dst_ndarray->itemsize` does not have to be set, it will be set to `src_ndarray->itemsize`
+    // - `dst_ndarray->shape` and `dst_ndarray.strides` can contain empty values
+    template <typename SizeT>
+    void subscript(SizeT num_subscripts, NDSubscript* subscripts, NDArray<SizeT>* src_ndarray, NDArray<SizeT>* dst_ndarray) {
+        // REFERENCE CODE (check out `_index_helper` in `__getitem__`):
+        //   https://github.com/wadetb/tinynumpy/blob/0d23d22e07062ffab2afa287374c7b366eebdda1/tinynumpy/tinynumpy.py#L652
+
+        // irrt_assert(dst_ndarray->ndims == ndarray::util::deduce_ndims_after_slicing(src_ndarray->ndims, num_subscripts, subscripts));
+
+        dst_ndarray->data = src_ndarray->data;
+        dst_ndarray->itemsize = src_ndarray->itemsize;
+
+        SizeT src_axis = 0;
+        SizeT dst_axis = 0;
+
+        for (SizeT i = 0; i < num_subscripts; i++) {
+            NDSubscript *ndsubscript = &subscripts[i];
+            if (ndsubscript->type == INPUT_SUBSCRIPT_TYPE_INDEX) {
+                // Handle when the ndsubscript is just a single (possibly negative) integer
+                // e.g., `my_array[::2, -5, ::-1]`
+                //                      ^^------ like this
+                SizeT index_user = *((SizeT*) ndsubscript->data);
+                SizeT index = slice::resolve_index_in_length(src_ndarray->shape[src_axis], index_user);
+                dst_ndarray->data += index * src_ndarray->strides[src_axis]; // Add offset
+
+                // Next
+                src_axis++;
+            } else if (ndsubscript->type == INPUT_SUBSCRIPT_TYPE_SLICE) {
+                // Handle when the ndsubscript is a slice (represented by UserSlice in IRRT)
+                // e.g., `my_array[::2, -5, ::-1]`
+                //                 ^^^------^^^^----- like these
+                UserSlice* user_slice = (UserSlice*) ndsubscript->data;
+
+                // TODO: use checked indices
+                Slice slice;
+                user_slice->indices(src_ndarray->shape[src_axis], &slice); // To resolve negative indices and other funny stuff written by the user
+
+                // NOTE: There is no need to write special code to handle negative steps/strides.
+                // This simple implementation meticulously handles both positive and negative steps/strides.
+                // Check out the tinynumpy and IRRT's test cases if you are not convinced.
+                dst_ndarray->data += (SizeT) slice.start * src_ndarray->strides[src_axis]; // Add offset (NOTE: no need to `* itemsize`, strides count in # of bytes)
+                dst_ndarray->strides[dst_axis] = ((SizeT) slice.step) * src_ndarray->strides[src_axis]; // Determine stride
+                dst_ndarray->shape[dst_axis] = (SizeT) slice.len(); // Determine shape dimension
+
+                // Next
+                dst_axis++;
+                src_axis++;
+            } else {
+                __builtin_unreachable();
+            }
+        }
+
+        /*
+            Reference python code:
+            ```python
+            dst_ndarray.shape.extend(src_ndarray.shape[src_axis:])
+            dst_ndarray.strides.extend(src_ndarray.strides[src_axis:])
+            ```
+        */
+
+        for (; dst_axis < dst_ndarray->ndims; dst_axis++, src_axis++) {
+            dst_ndarray->shape[dst_axis] = src_ndarray->shape[src_axis];
+            dst_ndarray->strides[dst_axis] = src_ndarray->strides[src_axis];
+        }
+    }
+}
+}
+
+extern "C" {
+void __nac3_ndarray_subscript(int32_t num_subscripts, NDSubscript* subscripts, NDArray<int32_t>* src_ndarray, NDArray<int32_t> *dst_ndarray) {
+    ndarray::subscript(num_subscripts, subscripts, src_ndarray, dst_ndarray);
+}
+
+void __nac3_ndarray_subscript64(int64_t num_subscripts, NDSubscript* subscripts, NDArray<int64_t>* src_ndarray, NDArray<int64_t> *dst_ndarray) {
+    ndarray::subscript(num_subscripts, subscripts, src_ndarray, dst_ndarray);
+}
+}

nac3core/irrt/irrt/slice.hpp

@@ -0,0 +1,132 @@
+#pragma once
+
+#include <irrt/int_defs.hpp>
+#include <irrt/slice.hpp>
+
+namespace {
+struct Slice {
+    SliceIndex start;
+    SliceIndex stop;
+    SliceIndex step;
+
+    // The length/The number of elements of the slice if it were a range,
+    // i.e., the value of `len(range(this->start, this->stop, this->end))`
+    SliceIndex len() {
+        SliceIndex diff = stop - start;
+        if (diff > 0 && step > 0) {
+            return ((diff - 1) / step) + 1;
+        } else if (diff < 0 && step < 0) {
+            return ((diff + 1) / step) + 1;
+        } else {
+            return 0;
+        }
+    }
+};
+
+namespace slice {
+    // "Resolve" an index value under a length in Python lists.
+    // If you have a `list` of length 100, `list[-1]` would resolve to `list[100-1] == list[99]`.
+    //
+    // If length == 0, this function returns 0
+    //
+    // If index is out of bounds, this function clamps the value
+    // (to `list[0]` or `list[-1]` in the context of a list and depending on if index is + or -)
+    SliceIndex resolve_index_in_length(SliceIndex length, SliceIndex index) {
+        if (index < 0) {
+            // Remember that index is negative, so do a plus here
+            return max<SliceIndex>(length + index, 0);
+        } else {
+            return min<SliceIndex>(length, index);
+        }
+    }
+}
+
+// A user-written Python-like slice.
+//
+// i.e., this slice is a triple of either an int or nothing. (e.g., `my_array[:10:2]`, `start` is None)
+//
+// You can "resolve" a `UserSlice` by using `UserSlice::indices(<length>)`
+struct UserSlice {
+    // Did the user specify `start`? If 0, `start` is undefined (and contains an empty value)
+    bool start_defined;
+    SliceIndex start;
+
+    // Similar to `start_defined`
+    bool stop_defined;
+    SliceIndex stop;
+
+    // Similar to `start_defined`
+    bool step_defined;
+    SliceIndex step;
+
+    // Constructor faithfully follows Python's `slice()`.
+    explicit UserSlice(SliceIndex stop) {
+        start_defined = false;
+        stop_defined = true;
+        step_defined = false;
+
+        this->stop = stop;
+    }
+
+    explicit UserSlice(SliceIndex start, SliceIndex stop) {
+        start_defined = true;
+        stop_defined = true;
+        step_defined = false;
+
+        this->start = start;
+        this->stop = stop;
+    }
+
+    explicit UserSlice(SliceIndex start, SliceIndex stop, SliceIndex step) {
+        start_defined = true;
+        stop_defined = true;
+        step_defined = true;
+
+        this->start = start;
+        this->stop = stop;
+        this->step = step;
+    }
+
+    // Like Python's `slice(start, stop, step).indices(length)`
+    void indices(SliceIndex length, Slice* result) {
+        // NOTE: This function implements Python's `slice.indices` *FAITHFULLY*.
+        // SEE: https://github.com/python/cpython/blob/f62161837e68c1c77961435f1b954412dd5c2b65/Objects/sliceobject.c#L546
+        result->step = step_defined ? step : 1;
+        bool step_is_negative = result->step < 0;
+
+        if (start_defined) {
+            result->start = slice::resolve_index_in_length(length, start);
+        } else {
+            result->start = step_is_negative ? length - 1 : 0;
+        }
+        
+        if (stop_defined) {
+            result->stop = slice::resolve_index_in_length(length, stop);
+        } else {
+            result->stop = step_is_negative ? -1 : length;
+        }
+    }
+
+    // `indices()` but asserts `this->step != 0` and `this->length >= 0`
+    void checked_indices(ErrorContext* errctx, SliceIndex length, Slice* result) {
+        if (!(length >= 0)) {
+            errctx->set_error(
+                errctx->error_ids->value_error,
+                "length should not be negative, got {0}", // Edited. Error message copied from python by doing `slice(0, 0, 0).indices(100)`
+                length
+            );
+            return;
+        }
+
+        if (!(this->step_defined && this->step != 0)) {
+            // Error message
+            errctx->set_error(
+                errctx->error_ids->value_error,
+                "slice step cannot be zero" // Error message copied from python by doing `slice(0, 0, 0).indices(100)`
+            );
+            return;
+        }
+        this->indices(length, result);
+    }
+};
+}

nac3core/irrt/irrt_everything.hpp

@@ -3,8 +3,10 @@
 #include <irrt/core.hpp>
 #include <irrt/error_context.hpp>
 #include <irrt/int_defs.hpp>
-#include <irrt/numpy/ndarray_def.hpp>
 #include <irrt/numpy/ndarray_basic.hpp>
 #include <irrt/numpy/ndarray_broadcast.hpp>
+#include <irrt/numpy/ndarray_def.hpp>
 #include <irrt/numpy/ndarray_fill.hpp>
+#include <irrt/numpy/ndarray_subscript.hpp>
+#include <irrt/slice.hpp>
 #include <irrt/utils.hpp>

nac3core/irrt/irrt_test.cpp

@@ -8,11 +8,13 @@
 #include <irrt_everything.hpp>
 
 #include <test/core.hpp>
-#include <test/ndarray.hpp>
 #include <test/test_core.hpp>
+#include <test/test_ndarray.hpp>
+#include <test/test_slice.hpp>
 
 int main() {
     test_int_exp();
     run_all_tests_ndarray();
+    run_all_tests_ndarray_slice();
     return 0;
 }

nac3core/irrt/test/test_ndarray.hpp

@@ -1,15 +1,14 @@
 #pragma once
 
 #include <test/core.hpp>
-#include <irrt/numpy/ndarray.hpp>
+#include <irrt_everything.hpp>
-#include <irrt/numpy/ndarray_util.hpp>
 
 void test_calc_size_from_shape_normal() {
     // Test shapes with normal values
     BEGIN_TEST();
 
     int32_t shape[4] = { 2, 3, 5, 7 };
-    assert_values_match(210, ndarray_util::calc_size_from_shape<int32_t>(4, shape));
+    assert_values_match(210, ndarray::util::calc_size_from_shape<int32_t>(4, shape));
 }
 
 void test_calc_size_from_shape_has_zero() {
@@ -17,7 +16,7 @@ void test_calc_size_from_shape_has_zero() {
     BEGIN_TEST();
 
     int32_t shape[4] = { 2, 0, 5, 7 };
-    assert_values_match(0, ndarray_util::calc_size_from_shape<int32_t>(4, shape));
+    assert_values_match(0, ndarray::util::calc_size_from_shape<int32_t>(4, shape));
 }
 
 void test_set_strides_by_shape() {
@@ -26,7 +25,7 @@ void test_set_strides_by_shape() {
 
     int32_t shape[4] = { 99, 3, 5, 7 };
     int32_t strides[4] = { 0 };
-    ndarray_util::set_strides_by_shape((int32_t) sizeof(int32_t), 4, strides, shape);
+    ndarray::util::set_strides_by_shape((int32_t) sizeof(int32_t), 4, strides, shape);
 
     int32_t expected_strides[4] = {
         105 * sizeof(int32_t),

nac3core/irrt/test/test_slice.hpp

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <test/core.hpp>
+#include <irrt_everything.hpp>
+
+void test_slice_1() {
+    BEGIN_TEST();
+
+    UserSlice user_slice(5);
+    Slice slice;
+    user_slice.indices(100, &slice);
+
+    assert_values_match(0, slice.start);
+    assert_values_match(5, slice.stop);
+    assert_values_match(1, slice.step);
+}
+
+void run_all_tests_ndarray_slice() {
+    test_slice_1();
+}