Abstract: A program is rerun up to an abnormal point. In this situation, a control flow at a division point between a normal point and the abnormal point is derived while a variable influencing the error and the value of the variable at the division point are derived on the basis of four dependences. A programmer determines an error of the control flow, an error of the value of the variable influencing the error, and an error of a value of a variable used in a conditional instruction/loop instruction. Such processing is repeated, so that an instruction finally remaining between the normal and abnormal points is determined to be a bug. If no instruction having a dependence on the abnormal point is present between the normal and abnormal points, a determination is made that a bug related to omission of an instruction is present between the normal and abnormal points.

Abstract: The inventive method calculates a position of the center of the eyeball as a fixed displacement from an origin of a facial coordinate system established by detection of three points on the face, and computes a vector therefrom to the center of the pupil. The vector and the detected position of the pupil are used to determine the visual axis.

Abstract: In a development portion (2) of a directed graph, when a program specification (1) is provided, descriptive elements having characteristics of sets described in the specification and descriptive elements defining a calculation method described therein are mapped with vertices and arcs based on descriptive elements defining a calculation method described therein are drawn between the vertices. Thus, the program specification is developed to the directed graph. The developed directed graph is analyzed by an analyzing portion (3) in view of the characteristics of sets and mappings and global characteristics of the directed graph, and arcs and vertices where flows of execution timing of the calculation synchronize and arcs and vertices where flows of execution timing of the calculation do not synchronize are detected.

Abstract: Characteristic features of images of an object eye are extracted to enable non-contact detection of eye movement. Two images of the eye are focused, and a differential image is generated to eliminate background noise and to permit feature extraction to be performed. In one feature of the invention, the illuminating light is polarized for use as a reference and the reflected light is separated to two light paths, each of which is focused to form an image of the object. In one path a polarizing plate blocks the regularly reflected light from the cornea so that only a diffused reflection component of the illuminating light from the other parts of the eye is passed, while in the other path both the regularly and diffusedly reflected light components are passed. A resulting differential image emphasizes the regular reflection component from the cornea relative to the background.